Calculus Examples

$lim_{x \to \infty} \frac{x^{2}}{2 x - 1} - \frac{x^{2}}{2 x + 1}$

Step 1

Combine terms.

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Step 1.1

To write $\frac{x^{2}}{2 x - 1}$ as a fraction with a common denominator, multiply by $\frac{2 x + 1}{2 x + 1}$ .

$lim_{x \to \infty} \frac{x^{2}}{2 x - 1} \cdot \frac{2 x + 1}{2 x + 1} - \frac{x^{2}}{2 x + 1}$

Step 1.2

To write $- \frac{x^{2}}{2 x + 1}$ as a fraction with a common denominator, multiply by $\frac{2 x - 1}{2 x - 1}$ .

$lim_{x \to \infty} \frac{x^{2}}{2 x - 1} \cdot \frac{2 x + 1}{2 x + 1} - \frac{x^{2}}{2 x + 1} \cdot \frac{2 x - 1}{2 x - 1}$

Step 1.3

Write each expression with a common denominator of $(2 x - 1) (2 x + 1)$ , by multiplying each by an appropriate factor of $1$ .

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Step 1.3.1

Multiply $\frac{x^{2}}{2 x - 1}$ by $\frac{2 x + 1}{2 x + 1}$ .

$lim_{x \to \infty} \frac{x^{2} (2 x + 1)}{(2 x - 1) (2 x + 1)} - \frac{x^{2}}{2 x + 1} \cdot \frac{2 x - 1}{2 x - 1}$

Step 1.3.2

Multiply $\frac{x^{2}}{2 x + 1}$ by $\frac{2 x - 1}{2 x - 1}$ .

$lim_{x \to \infty} \frac{x^{2} (2 x + 1)}{(2 x - 1) (2 x + 1)} - \frac{x^{2} (2 x - 1)}{(2 x + 1) (2 x - 1)}$

Step 1.3.3

Reorder the factors of $(2 x - 1) (2 x + 1)$ .

$lim_{x \to \infty} \frac{x^{2} (2 x + 1)}{(2 x + 1) (2 x - 1)} - \frac{x^{2} (2 x - 1)}{(2 x + 1) (2 x - 1)}$

Step 1.4

Combine the numerators over the common denominator.

$lim_{x \to \infty} \frac{x^{2} (2 x + 1) - x^{2} (2 x - 1)}{(2 x + 1) (2 x - 1)}$

Step 2

Apply L'Hospital's rule.

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Step 2.1

Evaluate the limit of the numerator and the limit of the denominator.

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Step 2.1.1

Take the limit of the numerator and the limit of the denominator.

$\frac{lim_{x \to \infty} x^{2} (2 x + 1) - x^{2} (2 x - 1)}{lim_{x \to \infty} (2 x + 1) (2 x - 1)}$

Step 2.1.2

Evaluate the limit of the numerator.

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Step 2.1.2.1

Apply the distributive property.

$\frac{lim_{x \to \infty} x^{2} (2 x) + x^{2} \cdot 1 - x^{2} (2 x - 1)}{lim_{x \to \infty} (2 x + 1) (2 x - 1)}$

Step 2.1.2.2

Apply the distributive property.

$\frac{lim_{x \to \infty} x^{2} (2 x) + x^{2} \cdot 1 - x^{2} (2 x) - x^{2} \cdot - 1}{lim_{x \to \infty} (2 x + 1) (2 x - 1)}$

Step 2.1.2.3

Simplify the expression.

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Step 2.1.2.3.1

Reorder $x^{2}$ and $2$ .

$\frac{lim_{x \to \infty} 2 \cdot x^{2} x + x^{2} \cdot 1 - x^{2} (2 x) - x^{2} \cdot - 1}{lim_{x \to \infty} (2 x + 1) (2 x - 1)}$

Step 2.1.2.3.2

Reorder $x^{2}$ and $1$ .

$\frac{lim_{x \to \infty} 2 \cdot x^{2} x + 1 \cdot x^{2} - x^{2} (2 x) - x^{2} \cdot - 1}{lim_{x \to \infty} (2 x + 1) (2 x - 1)}$

Step 2.1.2.3.3

Move $x^{2}$ .

$\frac{lim_{x \to \infty} 2 \cdot x^{2} x + 1 \cdot x^{2} - 1 \cdot 2 x^{2} x - x^{2} \cdot - 1}{lim_{x \to \infty} (2 x + 1) (2 x - 1)}$

Step 2.1.2.3.4

Move $x^{2}$ .

$\frac{lim_{x \to \infty} 2 \cdot x^{2} x + 1 \cdot x^{2} - 1 \cdot 2 x^{2} x - 1 \cdot - 1 x^{2}}{lim_{x \to \infty} (2 x + 1) (2 x - 1)}$

Step 2.1.2.4

Raise $x$ to the power of $1$ .

$\frac{lim_{x \to \infty} 2 (x^{2} x^{1}) + 1 x^{2} - 1 \cdot 2 x^{2} x - 1 \cdot - 1 x^{2}}{lim_{x \to \infty} (2 x + 1) (2 x - 1)}$

Step 2.1.2.5

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$\frac{lim_{x \to \infty} 2 x^{2 + 1} + 1 x^{2} - 1 \cdot 2 x^{2} x - 1 \cdot - 1 x^{2}}{lim_{x \to \infty} (2 x + 1) (2 x - 1)}$

Step 2.1.2.6

Add $2$ and $1$ .

$\frac{lim_{x \to \infty} 2 x^{3} + 1 x^{2} - 1 \cdot 2 x^{2} x - 1 \cdot - 1 x^{2}}{lim_{x \to \infty} (2 x + 1) (2 x - 1)}$

Step 2.1.2.7

Multiply $x^{2}$ by $1$ .

$\frac{lim_{x \to \infty} 2 x^{3} + x^{2} - 1 \cdot 2 x^{2} x - 1 \cdot - 1 x^{2}}{lim_{x \to \infty} (2 x + 1) (2 x - 1)}$

Step 2.1.2.8

Multiply $- 1$ by $2$ .

$\frac{lim_{x \to \infty} 2 x^{3} + x^{2} - 2 x^{2} x - 1 \cdot - 1 x^{2}}{lim_{x \to \infty} (2 x + 1) (2 x - 1)}$

Step 2.1.2.9

Raise $x$ to the power of $1$ .

$\frac{lim_{x \to \infty} 2 x^{3} + x^{2} - 2 (x^{2} x^{1}) - 1 \cdot - 1 x^{2}}{lim_{x \to \infty} (2 x + 1) (2 x - 1)}$

Step 2.1.2.10

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$\frac{lim_{x \to \infty} 2 x^{3} + x^{2} - 2 x^{2 + 1} - 1 \cdot - 1 x^{2}}{lim_{x \to \infty} (2 x + 1) (2 x - 1)}$

Step 2.1.2.11

Simplify by adding terms.

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Step 2.1.2.11.1

Add $2$ and $1$ .

$\frac{lim_{x \to \infty} 2 x^{3} + x^{2} - 2 x^{3} - 1 \cdot - 1 x^{2}}{lim_{x \to \infty} (2 x + 1) (2 x - 1)}$

Step 2.1.2.11.2

Simplify the expression.

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Step 2.1.2.11.2.1

Multiply $- 1$ by $- 1$ .

$\frac{lim_{x \to \infty} 2 x^{3} + x^{2} - 2 x^{3} + 1 x^{2}}{lim_{x \to \infty} (2 x + 1) (2 x - 1)}$

Step 2.1.2.11.2.2

Multiply $x^{2}$ by $1$ .

$\frac{lim_{x \to \infty} 2 x^{3} + x^{2} - 2 x^{3} + x^{2}}{lim_{x \to \infty} (2 x + 1) (2 x - 1)}$

Step 2.1.2.11.2.3

Move $x^{2}$ .

$\frac{lim_{x \to \infty} 2 x^{3} - 2 x^{3} + x^{2} + x^{2}}{lim_{x \to \infty} (2 x + 1) (2 x - 1)}$

Step 2.1.2.11.3

Subtract $2 x^{3}$ from $2 x^{3}$ .

$\frac{lim_{x \to \infty} 0 + x^{2} + x^{2}}{lim_{x \to \infty} (2 x + 1) (2 x - 1)}$

Step 2.1.2.11.4

Add $0$ and $x^{2}$ .

$\frac{lim_{x \to \infty} x^{2} + x^{2}}{lim_{x \to \infty} (2 x + 1) (2 x - 1)}$

Step 2.1.2.11.5

Add $x^{2}$ and $x^{2}$ .

$\frac{lim_{x \to \infty} 2 x^{2}}{lim_{x \to \infty} (2 x + 1) (2 x - 1)}$

Step 2.1.2.12

The limit at infinity of a polynomial whose leading coefficient is positive is infinity.

$\frac{\infty}{lim_{x \to \infty} (2 x + 1) (2 x - 1)}$

Step 2.1.3

Evaluate the limit of the denominator.

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Step 2.1.3.1

Apply the distributive property.

$\frac{\infty}{lim_{x \to \infty} 2 x (2 x - 1) + 1 (2 x - 1)}$

Step 2.1.3.2

Apply the distributive property.

$\frac{\infty}{lim_{x \to \infty} 2 x (2 x) + 2 x \cdot - 1 + 1 (2 x - 1)}$

Step 2.1.3.3

Apply the distributive property.

$\frac{\infty}{lim_{x \to \infty} 2 x (2 x) + 2 x \cdot - 1 + 1 (2 x) + 1 \cdot - 1}$

Step 2.1.3.4

Simplify the expression.

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Step 2.1.3.4.1

Move $x$ .

$\frac{\infty}{lim_{x \to \infty} 2 \cdot 2 x \cdot x + 2 x \cdot - 1 + 1 (2 x) + 1 \cdot - 1}$

Step 2.1.3.4.2

Move $x$ .

$\frac{\infty}{lim_{x \to \infty} 2 \cdot 2 x \cdot x + 2 \cdot - 1 x + 1 (2 x) + 1 \cdot - 1}$

Step 2.1.3.4.3

Multiply $2$ by $2$ .

$\frac{\infty}{lim_{x \to \infty} 4 x \cdot x + 2 \cdot - 1 x + 1 \cdot 2 x + 1 \cdot - 1}$

Step 2.1.3.5

Raise $x$ to the power of $1$ .

$\frac{\infty}{lim_{x \to \infty} 4 (x^{1} x) + 2 \cdot - 1 x + 1 \cdot 2 x + 1 \cdot - 1}$

Step 2.1.3.6

Raise $x$ to the power of $1$ .

$\frac{\infty}{lim_{x \to \infty} 4 (x^{1} x^{1}) + 2 \cdot - 1 x + 1 \cdot 2 x + 1 \cdot - 1}$

Step 2.1.3.7

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$\frac{\infty}{lim_{x \to \infty} 4 x^{1 + 1} + 2 \cdot - 1 x + 1 \cdot 2 x + 1 \cdot - 1}$

Step 2.1.3.8

Simplify by adding terms.

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Step 2.1.3.8.1

Add $1$ and $1$ .

$\frac{\infty}{lim_{x \to \infty} 4 x^{2} + 2 \cdot - 1 x + 1 \cdot 2 x + 1 \cdot - 1}$

Step 2.1.3.8.2

Multiply.

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Step 2.1.3.8.2.1

Multiply $2$ by $- 1$ .

$\frac{\infty}{lim_{x \to \infty} 4 x^{2} - 2 x + 1 \cdot 2 x + 1 \cdot - 1}$

Step 2.1.3.8.2.2

Simplify.

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Step 2.1.3.8.2.2.1

Multiply $2$ by $1$ .

$\frac{\infty}{lim_{x \to \infty} 4 x^{2} - 2 x + 2 x + 1 \cdot - 1}$

Step 2.1.3.8.2.2.2

Multiply $- 1$ by $1$ .

$\frac{\infty}{lim_{x \to \infty} 4 x^{2} - 2 x + 2 x - 1}$

Step 2.1.3.8.3

Add $- 2 x$ and $2 x$ .

$\frac{\infty}{lim_{x \to \infty} 4 x^{2} + 0 - 1}$

Step 2.1.3.8.4

Subtract $1$ from $0$ .

$\frac{\infty}{lim_{x \to \infty} 4 x^{2} - 1}$

Step 2.1.3.9

The limit at infinity of a polynomial whose leading coefficient is positive is infinity.

$\frac{\infty}{\infty}$

Step 2.1.3.10

Infinity divided by infinity is undefined.

Undefined

$\frac{\infty}{\infty}$

Step 2.1.4

Infinity divided by infinity is undefined.

Undefined

$\frac{\infty}{\infty}$

Step 2.2

Since $\frac{\infty}{\infty}$ is of indeterminate form, apply L'Hospital's Rule. L'Hospital's Rule states that the limit of a quotient of functions is equal to the limit of the quotient of their derivatives.

$lim_{x \to \infty} \frac{x^{2} (2 x + 1) - x^{2} (2 x - 1)}{(2 x + 1) (2 x - 1)} = lim_{x \to \infty} \frac{\frac{d}{d x} [x^{2} (2 x + 1) - x^{2} (2 x - 1)]}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3

Find the derivative of the numerator and denominator.

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Step 2.3.1

Differentiate the numerator and denominator.

$lim_{x \to \infty} \frac{\frac{d}{d x} [x^{2} (2 x + 1) - x^{2} (2 x - 1)]}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.2

By the Sum Rule, the derivative of $x^{2} (2 x + 1) - x^{2} (2 x - 1)$ with respect to $x$ is $\frac{d}{d x} [x^{2} (2 x + 1)] + \frac{d}{d x} [- x^{2} (2 x - 1)]$ .

$lim_{x \to \infty} \frac{\frac{d}{d x} [x^{2} (2 x + 1)] + \frac{d}{d x} [- x^{2} (2 x - 1)]}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.3

Evaluate $\frac{d}{d x} [x^{2} (2 x + 1)]$ .

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Step 2.3.3.1

Differentiate using the Product Rule which states that $\frac{d}{d x} [f (x) g (x)]$ is $f (x) \frac{d}{d x} [g (x)] + g (x) \frac{d}{d x} [f (x)]$ where $f (x) = x^{2}$ and $g (x) = 2 x + 1$ .

$lim_{x \to \infty} \frac{x^{2} \frac{d}{d x} [2 x + 1] + (2 x + 1) \frac{d}{d x} [x^{2}] + \frac{d}{d x} [- x^{2} (2 x - 1)]}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.3.2

By the Sum Rule, the derivative of $2 x + 1$ with respect to $x$ is $\frac{d}{d x} [2 x] + \frac{d}{d x} [1]$ .

$lim_{x \to \infty} \frac{x^{2} (\frac{d}{d x} [2 x] + \frac{d}{d x} [1]) + (2 x + 1) \frac{d}{d x} [x^{2}] + \frac{d}{d x} [- x^{2} (2 x - 1)]}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.3.3

Since $2$ is constant with respect to $x$ , the derivative of $2 x$ with respect to $x$ is $2 \frac{d}{d x} [x]$ .

$lim_{x \to \infty} \frac{x^{2} (2 \frac{d}{d x} [x] + \frac{d}{d x} [1]) + (2 x + 1) \frac{d}{d x} [x^{2}] + \frac{d}{d x} [- x^{2} (2 x - 1)]}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.3.4

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$lim_{x \to \infty} \frac{x^{2} (2 \cdot 1 + \frac{d}{d x} [1]) + (2 x + 1) \frac{d}{d x} [x^{2}] + \frac{d}{d x} [- x^{2} (2 x - 1)]}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.3.5

Since $1$ is constant with respect to $x$ , the derivative of $1$ with respect to $x$ is $0$ .

$lim_{x \to \infty} \frac{x^{2} (2 \cdot 1 + 0) + (2 x + 1) \frac{d}{d x} [x^{2}] + \frac{d}{d x} [- x^{2} (2 x - 1)]}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.3.6

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 2$ .

$lim_{x \to \infty} \frac{x^{2} (2 \cdot 1 + 0) + (2 x + 1) (2 x) + \frac{d}{d x} [- x^{2} (2 x - 1)]}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.3.7

Multiply $2$ by $1$ .

$lim_{x \to \infty} \frac{x^{2} (2 + 0) + (2 x + 1) (2 x) + \frac{d}{d x} [- x^{2} (2 x - 1)]}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.3.8

Add $2$ and $0$ .

$lim_{x \to \infty} \frac{x^{2} \cdot 2 + (2 x + 1) (2 x) + \frac{d}{d x} [- x^{2} (2 x - 1)]}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.3.9

Move $2$ to the left of $x^{2}$ .

$lim_{x \to \infty} \frac{2 \cdot x^{2} + (2 x + 1) (2 x) + \frac{d}{d x} [- x^{2} (2 x - 1)]}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.3.10

Move $2$ to the left of $2 x + 1$ .

$lim_{x \to \infty} \frac{2 x^{2} + 2 (2 x + 1) x + \frac{d}{d x} [- x^{2} (2 x - 1)]}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.4

Evaluate $\frac{d}{d x} [- x^{2} (2 x - 1)]$ .

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Step 2.3.4.1

Since $- 1$ is constant with respect to $x$ , the derivative of $- x^{2} (2 x - 1)$ with respect to $x$ is $- \frac{d}{d x} [x^{2} (2 x - 1)]$ .

$lim_{x \to \infty} \frac{2 x^{2} + 2 (2 x + 1) x - \frac{d}{d x} [x^{2} (2 x - 1)]}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.4.2

Differentiate using the Product Rule which states that $\frac{d}{d x} [f (x) g (x)]$ is $f (x) \frac{d}{d x} [g (x)] + g (x) \frac{d}{d x} [f (x)]$ where $f (x) = x^{2}$ and $g (x) = 2 x - 1$ .

$lim_{x \to \infty} \frac{2 x^{2} + 2 (2 x + 1) x - (x^{2} \frac{d}{d x} [2 x - 1] + (2 x - 1) \frac{d}{d x} [x^{2}])}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.4.3

By the Sum Rule, the derivative of $2 x - 1$ with respect to $x$ is $\frac{d}{d x} [2 x] + \frac{d}{d x} [- 1]$ .

$lim_{x \to \infty} \frac{2 x^{2} + 2 (2 x + 1) x - (x^{2} (\frac{d}{d x} [2 x] + \frac{d}{d x} [- 1]) + (2 x - 1) \frac{d}{d x} [x^{2}])}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.4.4

Since $2$ is constant with respect to $x$ , the derivative of $2 x$ with respect to $x$ is $2 \frac{d}{d x} [x]$ .

$lim_{x \to \infty} \frac{2 x^{2} + 2 (2 x + 1) x - (x^{2} (2 \frac{d}{d x} [x] + \frac{d}{d x} [- 1]) + (2 x - 1) \frac{d}{d x} [x^{2}])}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.4.5

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$lim_{x \to \infty} \frac{2 x^{2} + 2 (2 x + 1) x - (x^{2} (2 \cdot 1 + \frac{d}{d x} [- 1]) + (2 x - 1) \frac{d}{d x} [x^{2}])}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.4.6

Since $- 1$ is constant with respect to $x$ , the derivative of $- 1$ with respect to $x$ is $0$ .

$lim_{x \to \infty} \frac{2 x^{2} + 2 (2 x + 1) x - (x^{2} (2 \cdot 1 + 0) + (2 x - 1) \frac{d}{d x} [x^{2}])}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.4.7

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 2$ .

$lim_{x \to \infty} \frac{2 x^{2} + 2 (2 x + 1) x - (x^{2} (2 \cdot 1 + 0) + (2 x - 1) (2 x))}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.4.8

Multiply $2$ by $1$ .

$lim_{x \to \infty} \frac{2 x^{2} + 2 (2 x + 1) x - (x^{2} (2 + 0) + (2 x - 1) (2 x))}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.4.9

Add $2$ and $0$ .

$lim_{x \to \infty} \frac{2 x^{2} + 2 (2 x + 1) x - (x^{2} \cdot 2 + (2 x - 1) (2 x))}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.4.10

Move $2$ to the left of $x^{2}$ .

$lim_{x \to \infty} \frac{2 x^{2} + 2 (2 x + 1) x - (2 \cdot x^{2} + (2 x - 1) (2 x))}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.4.11

Move $2$ to the left of $2 x - 1$ .

$lim_{x \to \infty} \frac{2 x^{2} + 2 (2 x + 1) x - (2 x^{2} + 2 (2 x - 1) x)}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.5

Simplify.

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Step 2.3.5.1

Apply the distributive property.

$lim_{x \to \infty} \frac{2 x^{2} + (2 (2 x) + 2 \cdot 1) x - (2 x^{2} + 2 (2 x - 1) x)}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.5.2

Apply the distributive property.

$lim_{x \to \infty} \frac{2 x^{2} + 2 (2 x) x + 2 \cdot 1 x - (2 x^{2} + 2 (2 x - 1) x)}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.5.3

Apply the distributive property.

$lim_{x \to \infty} \frac{2 x^{2} + 2 (2 x) x + 2 \cdot 1 x - (2 x^{2} + (2 (2 x) + 2 \cdot - 1) x)}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.5.4

Apply the distributive property.

$lim_{x \to \infty} \frac{2 x^{2} + 2 (2 x) x + 2 \cdot 1 x - (2 x^{2} + 2 (2 x) x + 2 \cdot - 1 x)}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.5.5

Apply the distributive property.

$lim_{x \to \infty} \frac{2 x^{2} + 2 (2 x) x + 2 \cdot 1 x - (2 x^{2}) - (2 (2 x) x) - (2 \cdot - 1 x)}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.5.6

Combine terms.

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Step 2.3.5.6.1

Multiply $2$ by $2$ .

$lim_{x \to \infty} \frac{2 x^{2} + 4 x \cdot x + 2 \cdot 1 x - (2 x^{2}) - (2 (2 x) x) - (2 \cdot - 1 x)}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.5.6.2

Raise $x$ to the power of $1$ .

$lim_{x \to \infty} \frac{2 x^{2} + 4 (x^{1} x) + 2 \cdot 1 x - (2 x^{2}) - (2 (2 x) x) - (2 \cdot - 1 x)}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.5.6.3

Raise $x$ to the power of $1$ .

$lim_{x \to \infty} \frac{2 x^{2} + 4 (x^{1} x^{1}) + 2 \cdot 1 x - (2 x^{2}) - (2 (2 x) x) - (2 \cdot - 1 x)}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.5.6.4

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$lim_{x \to \infty} \frac{2 x^{2} + 4 x^{1 + 1} + 2 \cdot 1 x - (2 x^{2}) - (2 (2 x) x) - (2 \cdot - 1 x)}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.5.6.5

Add $1$ and $1$ .

$lim_{x \to \infty} \frac{2 x^{2} + 4 x^{2} + 2 \cdot 1 x - (2 x^{2}) - (2 (2 x) x) - (2 \cdot - 1 x)}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.5.6.6

Multiply $2$ by $1$ .

$lim_{x \to \infty} \frac{2 x^{2} + 4 x^{2} + 2 x - (2 x^{2}) - (2 (2 x) x) - (2 \cdot - 1 x)}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.5.6.7

Add $2 x^{2}$ and $4 x^{2}$ .

$lim_{x \to \infty} \frac{6 x^{2} + 2 x - (2 x^{2}) - (2 (2 x) x) - (2 \cdot - 1 x)}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.5.6.8

Multiply $2$ by $- 1$ .

$lim_{x \to \infty} \frac{6 x^{2} + 2 x - 2 x^{2} - (2 (2 x) x) - (2 \cdot - 1 x)}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.5.6.9

Multiply $2$ by $2$ .

$lim_{x \to \infty} \frac{6 x^{2} + 2 x - 2 x^{2} - (4 x \cdot x) - (2 \cdot - 1 x)}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.5.6.10

Raise $x$ to the power of $1$ .

$lim_{x \to \infty} \frac{6 x^{2} + 2 x - 2 x^{2} - (4 (x^{1} x)) - (2 \cdot - 1 x)}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.5.6.11

Raise $x$ to the power of $1$ .

$lim_{x \to \infty} \frac{6 x^{2} + 2 x - 2 x^{2} - (4 (x^{1} x^{1})) - (2 \cdot - 1 x)}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.5.6.12

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$lim_{x \to \infty} \frac{6 x^{2} + 2 x - 2 x^{2} - (4 x^{1 + 1}) - (2 \cdot - 1 x)}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.5.6.13

Add $1$ and $1$ .

$lim_{x \to \infty} \frac{6 x^{2} + 2 x - 2 x^{2} - (4 x^{2}) - (2 \cdot - 1 x)}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.5.6.14

Multiply $4$ by $- 1$ .

$lim_{x \to \infty} \frac{6 x^{2} + 2 x - 2 x^{2} - 4 x^{2} - (2 \cdot - 1 x)}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.5.6.15

Multiply $2$ by $- 1$ .

$lim_{x \to \infty} \frac{6 x^{2} + 2 x - 2 x^{2} - 4 x^{2} - (- 2 x)}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.5.6.16

Multiply $- 2$ by $- 1$ .

$lim_{x \to \infty} \frac{6 x^{2} + 2 x - 2 x^{2} - 4 x^{2} + 2 x}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.5.6.17

Subtract $4 x^{2}$ from $- 2 x^{2}$ .

$lim_{x \to \infty} \frac{6 x^{2} + 2 x - 6 x^{2} + 2 x}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.5.6.18

Subtract $6 x^{2}$ from $6 x^{2}$ .

$lim_{x \to \infty} \frac{2 x + 0 + 2 x}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.5.6.19

Add $2 x$ and $0$ .

$lim_{x \to \infty} \frac{2 x + 2 x}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.5.6.20

Add $2 x$ and $2 x$ .

$lim_{x \to \infty} \frac{4 x}{\frac{d}{d x} [(2 x + 1) (2 x - 1)]}$

Step 2.3.6

Differentiate using the Product Rule which states that $\frac{d}{d x} [f (x) g (x)]$ is $f (x) \frac{d}{d x} [g (x)] + g (x) \frac{d}{d x} [f (x)]$ where $f (x) = 2 x + 1$ and $g (x) = 2 x - 1$ .

$lim_{x \to \infty} \frac{4 x}{(2 x + 1) \frac{d}{d x} [2 x - 1] + (2 x - 1) \frac{d}{d x} [2 x + 1]}$

Step 2.3.7

By the Sum Rule, the derivative of $2 x - 1$ with respect to $x$ is $\frac{d}{d x} [2 x] + \frac{d}{d x} [- 1]$ .

$lim_{x \to \infty} \frac{4 x}{(2 x + 1) (\frac{d}{d x} [2 x] + \frac{d}{d x} [- 1]) + (2 x - 1) \frac{d}{d x} [2 x + 1]}$

Step 2.3.8

Since $2$ is constant with respect to $x$ , the derivative of $2 x$ with respect to $x$ is $2 \frac{d}{d x} [x]$ .

$lim_{x \to \infty} \frac{4 x}{(2 x + 1) (2 \frac{d}{d x} [x] + \frac{d}{d x} [- 1]) + (2 x - 1) \frac{d}{d x} [2 x + 1]}$

Step 2.3.9

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$lim_{x \to \infty} \frac{4 x}{(2 x + 1) (2 \cdot 1 + \frac{d}{d x} [- 1]) + (2 x - 1) \frac{d}{d x} [2 x + 1]}$

Step 2.3.10

Multiply $2$ by $1$ .

$lim_{x \to \infty} \frac{4 x}{(2 x + 1) (2 + \frac{d}{d x} [- 1]) + (2 x - 1) \frac{d}{d x} [2 x + 1]}$

Step 2.3.11

Since $- 1$ is constant with respect to $x$ , the derivative of $- 1$ with respect to $x$ is $0$ .

$lim_{x \to \infty} \frac{4 x}{(2 x + 1) (2 + 0) + (2 x - 1) \frac{d}{d x} [2 x + 1]}$

Step 2.3.12

Add $2$ and $0$ .

$lim_{x \to \infty} \frac{4 x}{(2 x + 1) \cdot 2 + (2 x - 1) \frac{d}{d x} [2 x + 1]}$

Step 2.3.13

Move $2$ to the left of $2 x + 1$ .

$lim_{x \to \infty} \frac{4 x}{2 \cdot (2 x + 1) + (2 x - 1) \frac{d}{d x} [2 x + 1]}$

Step 2.3.14

By the Sum Rule, the derivative of $2 x + 1$ with respect to $x$ is $\frac{d}{d x} [2 x] + \frac{d}{d x} [1]$ .

$lim_{x \to \infty} \frac{4 x}{2 (2 x + 1) + (2 x - 1) (\frac{d}{d x} [2 x] + \frac{d}{d x} [1])}$

Step 2.3.15

Since $2$ is constant with respect to $x$ , the derivative of $2 x$ with respect to $x$ is $2 \frac{d}{d x} [x]$ .

$lim_{x \to \infty} \frac{4 x}{2 (2 x + 1) + (2 x - 1) (2 \frac{d}{d x} [x] + \frac{d}{d x} [1])}$

Step 2.3.16

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$lim_{x \to \infty} \frac{4 x}{2 (2 x + 1) + (2 x - 1) (2 \cdot 1 + \frac{d}{d x} [1])}$

Step 2.3.17

Multiply $2$ by $1$ .

$lim_{x \to \infty} \frac{4 x}{2 (2 x + 1) + (2 x - 1) (2 + \frac{d}{d x} [1])}$

Step 2.3.18

Since $1$ is constant with respect to $x$ , the derivative of $1$ with respect to $x$ is $0$ .

$lim_{x \to \infty} \frac{4 x}{2 (2 x + 1) + (2 x - 1) (2 + 0)}$

Step 2.3.19

Add $2$ and $0$ .

$lim_{x \to \infty} \frac{4 x}{2 (2 x + 1) + (2 x - 1) \cdot 2}$

Step 2.3.20

Move $2$ to the left of $2 x - 1$ .

$lim_{x \to \infty} \frac{4 x}{2 (2 x + 1) + 2 \cdot (2 x - 1)}$

Step 2.3.21

Simplify.

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Step 2.3.21.1

Apply the distributive property.

$lim_{x \to \infty} \frac{4 x}{2 (2 x) + 2 \cdot 1 + 2 (2 x - 1)}$

Step 2.3.21.2

Apply the distributive property.

$lim_{x \to \infty} \frac{4 x}{2 (2 x) + 2 \cdot 1 + 2 (2 x) + 2 \cdot - 1}$

Step 2.3.21.3

Combine terms.

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Step 2.3.21.3.1

Multiply $2$ by $2$ .

$lim_{x \to \infty} \frac{4 x}{4 x + 2 \cdot 1 + 2 (2 x) + 2 \cdot - 1}$

Step 2.3.21.3.2

Multiply $2$ by $1$ .

$lim_{x \to \infty} \frac{4 x}{4 x + 2 + 2 (2 x) + 2 \cdot - 1}$

Step 2.3.21.3.3

Multiply $2$ by $2$ .

$lim_{x \to \infty} \frac{4 x}{4 x + 2 + 4 x + 2 \cdot - 1}$

Step 2.3.21.3.4

Multiply $2$ by $- 1$ .

$lim_{x \to \infty} \frac{4 x}{4 x + 2 + 4 x - 2}$

Step 2.3.21.3.5

Add $4 x$ and $4 x$ .

$lim_{x \to \infty} \frac{4 x}{8 x + 2 - 2}$

Step 2.3.21.3.6

Subtract $2$ from $2$ .

$lim_{x \to \infty} \frac{4 x}{8 x + 0}$

Step 2.3.21.3.7

Add $8 x$ and $0$ .

$lim_{x \to \infty} \frac{4 x}{8 x}$

Step 2.4

Reduce.

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Step 2.4.1

Cancel the common factor of $4$ and $8$ .

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Step 2.4.1.1

Factor $4$ out of $4 x$ .

$lim_{x \to \infty} \frac{4 (x)}{8 x}$

Step 2.4.1.2

Cancel the common factors.

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Step 2.4.1.2.1

Factor $4$ out of $8 x$ .

$lim_{x \to \infty} \frac{4 (x)}{4 (2 x)}$

Step 2.4.1.2.2

Cancel the common factor.

$lim_{x \to \infty} \frac{4 x}{4 (2 x)}$

Step 2.4.1.2.3

Rewrite the expression.

$lim_{x \to \infty} \frac{x}{2 x}$

Step 2.4.2

Cancel the common factor of $x$ .

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Step 2.4.2.1

Cancel the common factor.

$lim_{x \to \infty} \frac{x}{2 x}$

Step 2.4.2.2

Rewrite the expression.

$lim_{x \to \infty} \frac{1}{2}$

Step 3

Evaluate the limit of $\frac{1}{2}$ which is constant as $x$ approaches $\infty$ .

$\frac{1}{2}$

Step 4

The result can be shown in multiple forms.

Exact Form:

$\frac{1}{2}$

Decimal Form:

$0.5$