Calculus Examples

$z = x^{3} + \frac{x^{2}}{1 - x - 4 x^{2}}$

Step 1

Differentiate both sides of the equation.

$\frac{d}{d x} (z) = \frac{d}{d x} (x^{3} + \frac{x^{2}}{1 - x - 4 x^{2}})$

Step 2

The derivative of $z$ with respect to $x$ is $z'$ .

$z'$

Step 3

Differentiate the right side of the equation.

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Step 3.1

Differentiate.

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Step 3.1.1

By the Sum Rule, the derivative of $x^{3} + \frac{x^{2}}{1 - x - 4 x^{2}}$ with respect to $x$ is $\frac{d}{d x} [x^{3}] + \frac{d}{d x} [\frac{x^{2}}{1 - x - 4 x^{2}}]$ .

$\frac{d}{d x} [x^{3}] + \frac{d}{d x} [\frac{x^{2}}{1 - x - 4 x^{2}}]$

Step 3.1.2

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 3$ .

$3 x^{2} + \frac{d}{d x} [\frac{x^{2}}{1 - x - 4 x^{2}}]$

Step 3.2

Evaluate $\frac{d}{d x} [\frac{x^{2}}{1 - x - 4 x^{2}}]$ .

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Step 3.2.1

Differentiate using the Quotient Rule which states that $\frac{d}{d x} [\frac{f (x)}{g (x)}]$ is $\frac{g (x) \frac{d}{d x} [f (x)] - f (x) \frac{d}{d x} [g (x)]}{{g (x)}^{2}}$ where $f (x) = x^{2}$ and $g (x) = 1 - x - 4 x^{2}$ .

$3 x^{2} + \frac{(1 - x - 4 x^{2}) \frac{d}{d x} [x^{2}] - x^{2} \frac{d}{d x} [1 - x - 4 x^{2}]}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.2.2

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

$3 x^{2} + \frac{(1 - x - 4 x^{2}) (2 x) - x^{2} \frac{d}{d x} [1 - x - 4 x^{2}]}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.2.3

By the Sum Rule, the derivative of $1 - x - 4 x^{2}$ with respect to $x$ is $\frac{d}{d x} [1] + \frac{d}{d x} [- x] + \frac{d}{d x} [- 4 x^{2}]$ .

$3 x^{2} + \frac{(1 - x - 4 x^{2}) (2 x) - x^{2} (\frac{d}{d x} [1] + \frac{d}{d x} [- x] + \frac{d}{d x} [- 4 x^{2}])}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.2.4

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

$3 x^{2} + \frac{(1 - x - 4 x^{2}) (2 x) - x^{2} (0 + \frac{d}{d x} [- x] + \frac{d}{d x} [- 4 x^{2}])}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.2.5

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

$3 x^{2} + \frac{(1 - x - 4 x^{2}) (2 x) - x^{2} (0 - \frac{d}{d x} [x] + \frac{d}{d x} [- 4 x^{2}])}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.2.6

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

$3 x^{2} + \frac{(1 - x - 4 x^{2}) (2 x) - x^{2} (0 - 1 \cdot 1 + \frac{d}{d x} [- 4 x^{2}])}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.2.7

Since $- 4$ is constant with respect to $x$ , the derivative of $- 4 x^{2}$ with respect to $x$ is $- 4 \frac{d}{d x} [x^{2}]$ .

$3 x^{2} + \frac{(1 - x - 4 x^{2}) (2 x) - x^{2} (0 - 1 \cdot 1 - 4 \frac{d}{d x} [x^{2}])}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.2.8

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

$3 x^{2} + \frac{(1 - x - 4 x^{2}) (2 x) - x^{2} (0 - 1 \cdot 1 - 4 (2 x))}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.2.9

Move $2$ to the left of $1 - x - 4 x^{2}$ .

$3 x^{2} + \frac{2 \cdot (1 - x - 4 x^{2}) x - x^{2} (0 - 1 \cdot 1 - 4 (2 x))}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.2.10

Multiply $- 1$ by $1$ .

$3 x^{2} + \frac{2 (1 - x - 4 x^{2}) x - x^{2} (0 - 1 - 4 (2 x))}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.2.11

Subtract $1$ from $0$ .

$3 x^{2} + \frac{2 (1 - x - 4 x^{2}) x - x^{2} (- 1 - 4 (2 x))}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.2.12

Multiply $2$ by $- 4$ .

$3 x^{2} + \frac{2 (1 - x - 4 x^{2}) x - x^{2} (- 1 - 8 x)}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.3

Simplify.

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Step 3.3.1

Apply the distributive property.

$3 x^{2} + \frac{(2 \cdot 1 + 2 (- x) + 2 (- 4 x^{2})) x - x^{2} (- 1 - 8 x)}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.3.2

Apply the distributive property.

$3 x^{2} + \frac{2 \cdot 1 x + 2 (- x) x + 2 (- 4 x^{2}) x - x^{2} (- 1 - 8 x)}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.3.3

Apply the distributive property.

$3 x^{2} + \frac{2 \cdot 1 x + 2 (- x) x + 2 (- 4 x^{2}) x - x^{2} \cdot - 1 - x^{2} (- 8 x)}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.3.4

Combine terms.

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Step 3.3.4.1

Multiply $2$ by $1$ .

$3 x^{2} + \frac{2 x + 2 (- x) x + 2 (- 4 x^{2}) x - x^{2} \cdot - 1 - x^{2} (- 8 x)}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.3.4.2

Multiply $- 1$ by $2$ .

$3 x^{2} + \frac{2 x - 2 x \cdot x + 2 (- 4 x^{2}) x - x^{2} \cdot - 1 - x^{2} (- 8 x)}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.3.4.3

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

$3 x^{2} + \frac{2 x - 2 (x^{1} x) + 2 (- 4 x^{2}) x - x^{2} \cdot - 1 - x^{2} (- 8 x)}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.3.4.4

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

$3 x^{2} + \frac{2 x - 2 (x^{1} x^{1}) + 2 (- 4 x^{2}) x - x^{2} \cdot - 1 - x^{2} (- 8 x)}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.3.4.5

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

$3 x^{2} + \frac{2 x - 2 x^{1 + 1} + 2 (- 4 x^{2}) x - x^{2} \cdot - 1 - x^{2} (- 8 x)}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.3.4.6

Add $1$ and $1$ .

$3 x^{2} + \frac{2 x - 2 x^{2} + 2 (- 4 x^{2}) x - x^{2} \cdot - 1 - x^{2} (- 8 x)}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.3.4.7

Multiply $- 4$ by $2$ .

$3 x^{2} + \frac{2 x - 2 x^{2} - 8 x^{2} x - x^{2} \cdot - 1 - x^{2} (- 8 x)}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.3.4.8

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

$3 x^{2} + \frac{2 x - 2 x^{2} - 8 (x^{1} x^{2}) - x^{2} \cdot - 1 - x^{2} (- 8 x)}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.3.4.9

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

$3 x^{2} + \frac{2 x - 2 x^{2} - 8 x^{1 + 2} - x^{2} \cdot - 1 - x^{2} (- 8 x)}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.3.4.10

Add $1$ and $2$ .

$3 x^{2} + \frac{2 x - 2 x^{2} - 8 x^{3} - x^{2} \cdot - 1 - x^{2} (- 8 x)}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.3.4.11

Multiply $- 1$ by $- 1$ .

$3 x^{2} + \frac{2 x - 2 x^{2} - 8 x^{3} + 1 x^{2} - x^{2} (- 8 x)}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.3.4.12

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

$3 x^{2} + \frac{2 x - 2 x^{2} - 8 x^{3} + x^{2} - x^{2} (- 8 x)}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.3.4.13

Multiply $- 8$ by $- 1$ .

$3 x^{2} + \frac{2 x - 2 x^{2} - 8 x^{3} + x^{2} + 8 x^{2} x}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.3.4.14

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

$3 x^{2} + \frac{2 x - 2 x^{2} - 8 x^{3} + x^{2} + 8 (x^{1} x^{2})}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.3.4.15

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

$3 x^{2} + \frac{2 x - 2 x^{2} - 8 x^{3} + x^{2} + 8 x^{1 + 2}}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.3.4.16

Add $1$ and $2$ .

$3 x^{2} + \frac{2 x - 2 x^{2} - 8 x^{3} + x^{2} + 8 x^{3}}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.3.4.17

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

$3 x^{2} + \frac{2 x - 8 x^{3} - x^{2} + 8 x^{3}}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.3.4.18

Add $- 8 x^{3}$ and $8 x^{3}$ .

$3 x^{2} + \frac{2 x - x^{2} + 0}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.3.4.19

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

$3 x^{2} + \frac{2 x - x^{2}}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.3.4.20

To write $3 x^{2}$ as a fraction with a common denominator, multiply by $\frac{{(1 - x - 4 x^{2})}^{2}}{{(1 - x - 4 x^{2})}^{2}}$ .

$\frac{3 x^{2} {(1 - x - 4 x^{2})}^{2}}{{(1 - x - 4 x^{2})}^{2}} + \frac{2 x - x^{2}}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.3.4.21

Combine the numerators over the common denominator.

$\frac{3 x^{2} {(1 - x - 4 x^{2})}^{2} + 2 x - x^{2}}{{(1 - x - 4 x^{2})}^{2}}$

Step 3.3.5

Reorder terms.

$\frac{- x^{2} + 3 x^{2} {(1 - x - 4 x^{2})}^{2} + 2 x}{{(- 4 x^{2} - x + 1)}^{2}}$

Step 4

Reform the equation by setting the left side equal to the right side.

$z' = \frac{- x^{2} + 3 x^{2} {(1 - x - 4 x^{2})}^{2} + 2 x}{{(- 4 x^{2} - x + 1)}^{2}}$

Step 5

Replace $z'$ with $\frac{d z}{d x}$ .

$\frac{d z}{d x} = \frac{- x^{2} + 3 x^{2} {(1 - x - 4 x^{2})}^{2} + 2 x}{{(- 4 x^{2} - x + 1)}^{2}}$