Calculus Examples

$f (x) = \frac{2 x}{1 + x^{2}}$

Step 1

Find the first derivative.

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Step 1.1

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

$f' (x) = 2 \frac{d}{d x} (\frac{x}{1 + x^{2}})$

Step 1.2

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 $f (x) = x$ and $g (x) = 1 + x^{2}$ .

$f' (x) = 2 (\frac{(1 + x^{2}) \frac{d}{d x} (x) - x \frac{d}{d x} (1 + x^{2})}{{(1 + x^{2})}^{2}})$

Step 1.3

Differentiate.

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Step 1.3.1

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

$f' (x) = 2 (\frac{(1 + x^{2}) \cdot 1 - x \frac{d}{d x} (1 + x^{2})}{{(1 + x^{2})}^{2}})$

Step 1.3.2

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

$f' (x) = 2 (\frac{1 + x^{2} - x \frac{d}{d x} (1 + x^{2})}{{(1 + x^{2})}^{2}})$

Step 1.3.3

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

$f' (x) = 2 (\frac{1 + x^{2} - x (\frac{d}{d x} (1) + \frac{d}{d x} (x^{2}))}{{(1 + x^{2})}^{2}})$

Step 1.3.4

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

$f' (x) = 2 (\frac{1 + x^{2} - x (0 + \frac{d}{d x} (x^{2}))}{{(1 + x^{2})}^{2}})$

Step 1.3.5

Add $0$ and $\frac{d}{d x} [x^{2}]$ .

$f' (x) = 2 (\frac{1 + x^{2} - x \frac{d}{d x} x^{2}}{{(1 + x^{2})}^{2}})$

Step 1.3.6

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

$f' (x) = 2 (\frac{1 + x^{2} - x (2 x)}{{(1 + x^{2})}^{2}})$

Step 1.3.7

Multiply $2$ by $- 1$ .

$f' (x) = 2 (\frac{1 + x^{2} - 2 x \cdot x}{{(1 + x^{2})}^{2}})$

Step 1.4

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

$f' (x) = 2 (\frac{1 + x^{2} - 2 (x \cdot x)}{{(1 + x^{2})}^{2}})$

Step 1.5

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

$f' (x) = 2 (\frac{1 + x^{2} - 2 (x \cdot x)}{{(1 + x^{2})}^{2}})$

Step 1.6

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

$f' (x) = 2 (\frac{1 + x^{2} - 2 x^{1 + 1}}{{(1 + x^{2})}^{2}})$

Step 1.7

Add $1$ and $1$ .

$f' (x) = 2 (\frac{1 + x^{2} - 2 x^{2}}{{(1 + x^{2})}^{2}})$

Step 1.8

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

$f' (x) = 2 (\frac{1 - x^{2}}{{(1 + x^{2})}^{2}})$

Step 1.9

Combine $2$ and $\frac{1 - x^{2}}{{(1 + x^{2})}^{2}}$ .

$f' (x) = \frac{2 (1 - x^{2})}{{(1 + x^{2})}^{2}}$

Step 1.10

Simplify.

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Step 1.10.1

Apply the distributive property.

$f' (x) = \frac{2 \cdot 1 + 2 (- x^{2})}{{(1 + x^{2})}^{2}}$

Step 1.10.2

Simplify each term.

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Step 1.10.2.1

Multiply $2$ by $1$ .

$f' (x) = \frac{2 + 2 (- x^{2})}{{(1 + x^{2})}^{2}}$

Step 1.10.2.2

Multiply $- 1$ by $2$ .

$f' (x) = \frac{2 - 2 x^{2}}{{(1 + x^{2})}^{2}}$

Step 1.10.3

Reorder terms.

$f' (x) = \frac{- 2 x^{2} + 2}{{(x^{2} + 1)}^{2}}$

Step 2

Find the second derivative.

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Step 2.1

$f'' (x) = \frac{{(x^{2} + 1)}^{2} \frac{d}{d x} (- 2 x^{2} + 2) - (- 2 x^{2} + 2) \frac{d}{d x} {(x^{2} + 1)}^{2}}{{({(x^{2} + 1)}^{2})}^{2}}$

Step 2.2

Differentiate.

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Step 2.2.1

Multiply the exponents in ${({(x^{2} + 1)}^{2})}^{2}$ .

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Step 2.2.1.1

Apply the power rule and multiply exponents, ${(a^{m})}^{n} = a^{m n}$ .

$f'' (x) = \frac{{(x^{2} + 1)}^{2} \frac{d}{d x} (- 2 x^{2} + 2) - (- 2 x^{2} + 2) \frac{d}{d x} {(x^{2} + 1)}^{2}}{{(x^{2} + 1)}^{2 \cdot 2}}$

Step 2.2.1.2

Multiply $2$ by $2$ .

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

Step 2.2.2

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

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

Step 2.2.3

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

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

Step 2.2.4

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

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

Step 2.2.5

Multiply $2$ by $- 2$ .

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

Step 2.2.6

Since $2$ is constant with respect to $x$ , the derivative of $2$ with respect to $x$ is $0$ .

$f'' (x) = \frac{{(x^{2} + 1)}^{2} (- 4 x + 0) - (- 2 x^{2} + 2) \frac{d}{d x} {(x^{2} + 1)}^{2}}{{(x^{2} + 1)}^{4}}$

Step 2.2.7

Add $- 4 x$ and $0$ .

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

Step 2.3

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

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Step 2.3.1

To apply the Chain Rule, set $u$ as $x^{2} + 1$ .

$f'' (x) = \frac{{(x^{2} + 1)}^{2} (- 4 x) - (- 2 x^{2} + 2) (\frac{d}{d u} (u^{2}) \frac{d}{d x} (x^{2} + 1))}{{(x^{2} + 1)}^{4}}$

Step 2.3.2

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

$f'' (x) = \frac{{(x^{2} + 1)}^{2} (- 4 x) - (- 2 x^{2} + 2) (2 u \frac{d}{d x} (x^{2} + 1))}{{(x^{2} + 1)}^{4}}$

Step 2.3.3

Replace all occurrences of $u$ with $x^{2} + 1$ .

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

Step 2.4

Differentiate.

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Step 2.4.1

Multiply $2$ by $- 1$ .

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

Step 2.4.2

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

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

Step 2.4.3

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

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

Step 2.4.4

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

$f'' (x) = \frac{{(x^{2} + 1)}^{2} (- 4 x) - 2 (- 2 x^{2} + 2) ((x^{2} + 1) (2 x + 0))}{{(x^{2} + 1)}^{4}}$

Step 2.4.5

Simplify the expression.

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Step 2.4.5.1

Add $2 x$ and $0$ .

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

Step 2.4.5.2

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

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

Step 2.4.5.3

Multiply $2$ by $- 2$ .

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

Step 2.5

Simplify.

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Step 2.5.1

Apply the distributive property.

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

Step 2.5.2

Apply the distributive property.

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

Step 2.5.3

Simplify the numerator.

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Step 2.5.3.1

Simplify each term.

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Step 2.5.3.1.1

Rewrite using the commutative property of multiplication.

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

Step 2.5.3.1.2

Rewrite ${(x^{2} + 1)}^{2}$ as $(x^{2} + 1) (x^{2} + 1)$ .

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

Step 2.5.3.1.3

Expand $(x^{2} + 1) (x^{2} + 1)$ using the FOIL Method.

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Step 2.5.3.1.3.1

Apply the distributive property.

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

Step 2.5.3.1.3.2

Apply the distributive property.

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

Step 2.5.3.1.3.3

Apply the distributive property.

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

Step 2.5.3.1.4

Simplify and combine like terms.

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Step 2.5.3.1.4.1

Simplify each term.

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Step 2.5.3.1.4.1.1

Multiply $x^{2}$ by $x^{2}$ by adding the exponents.

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Step 2.5.3.1.4.1.1.1

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

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

Step 2.5.3.1.4.1.1.2

Add $2$ and $2$ .

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

Step 2.5.3.1.4.1.2

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

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

Step 2.5.3.1.4.1.3

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

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

Step 2.5.3.1.4.1.4

Multiply $1$ by $1$ .

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

Step 2.5.3.1.4.2

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

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

Step 2.5.3.1.5

Apply the distributive property.

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

Step 2.5.3.1.6

Simplify.

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Step 2.5.3.1.6.1

Multiply $2$ by $- 4$ .

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

Step 2.5.3.1.6.2

Multiply $- 4$ by $1$ .

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

Step 2.5.3.1.7

Apply the distributive property.

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

Step 2.5.3.1.8

Simplify.

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Step 2.5.3.1.8.1

Multiply $x^{4}$ by $x$ by adding the exponents.

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Step 2.5.3.1.8.1.1

Move $x$ .

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

Step 2.5.3.1.8.1.2

Multiply $x$ by $x^{4}$ .

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Step 2.5.3.1.8.1.2.1

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

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

Step 2.5.3.1.8.1.2.2

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

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

Step 2.5.3.1.8.1.3

Add $1$ and $4$ .

$f'' (x) = \frac{- 4 x^{5} - 8 x^{2} x - 4 x + (- 4 (- 2 x^{2}) - 4 \cdot 2) (x^{2} x + 1 x)}{{(x^{2} + 1)}^{4}}$

Step 2.5.3.1.8.2

Multiply $x^{2}$ by $x$ by adding the exponents.

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Step 2.5.3.1.8.2.1

Move $x$ .

$f'' (x) = \frac{- 4 x^{5} - 8 (x \cdot x^{2}) - 4 x + (- 4 (- 2 x^{2}) - 4 \cdot 2) (x^{2} x + 1 x)}{{(x^{2} + 1)}^{4}}$

Step 2.5.3.1.8.2.2

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

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Step 2.5.3.1.8.2.2.1

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

$f'' (x) = \frac{- 4 x^{5} - 8 (x \cdot x^{2}) - 4 x + (- 4 (- 2 x^{2}) - 4 \cdot 2) (x^{2} x + 1 x)}{{(x^{2} + 1)}^{4}}$

Step 2.5.3.1.8.2.2.2

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

$f'' (x) = \frac{- 4 x^{5} - 8 x^{1 + 2} - 4 x + (- 4 (- 2 x^{2}) - 4 \cdot 2) (x^{2} x + 1 x)}{{(x^{2} + 1)}^{4}}$

Step 2.5.3.1.8.2.3

Add $1$ and $2$ .

$f'' (x) = \frac{- 4 x^{5} - 8 x^{3} - 4 x + (- 4 (- 2 x^{2}) - 4 \cdot 2) (x^{2} x + 1 x)}{{(x^{2} + 1)}^{4}}$

Step 2.5.3.1.9

Simplify each term.

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Step 2.5.3.1.9.1

Multiply $- 2$ by $- 4$ .

$f'' (x) = \frac{- 4 x^{5} - 8 x^{3} - 4 x + (8 x^{2} - 4 \cdot 2) (x^{2} x + 1 x)}{{(x^{2} + 1)}^{4}}$

Step 2.5.3.1.9.2

Multiply $- 4$ by $2$ .

$f'' (x) = \frac{- 4 x^{5} - 8 x^{3} - 4 x + (8 x^{2} - 8) (x^{2} x + 1 x)}{{(x^{2} + 1)}^{4}}$

Step 2.5.3.1.10

Simplify each term.

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Step 2.5.3.1.10.1

Multiply $x^{2}$ by $x$ by adding the exponents.

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Step 2.5.3.1.10.1.1

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

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Step 2.5.3.1.10.1.1.1

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

$f'' (x) = \frac{- 4 x^{5} - 8 x^{3} - 4 x + (8 x^{2} - 8) (x^{2} x + 1 x)}{{(x^{2} + 1)}^{4}}$

Step 2.5.3.1.10.1.1.2

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

$f'' (x) = \frac{- 4 x^{5} - 8 x^{3} - 4 x + (8 x^{2} - 8) (x^{2 + 1} + 1 x)}{{(x^{2} + 1)}^{4}}$

Step 2.5.3.1.10.1.2

Add $2$ and $1$ .

$f'' (x) = \frac{- 4 x^{5} - 8 x^{3} - 4 x + (8 x^{2} - 8) (x^{3} + 1 x)}{{(x^{2} + 1)}^{4}}$

Step 2.5.3.1.10.2

Multiply $x$ by $1$ .

$f'' (x) = \frac{- 4 x^{5} - 8 x^{3} - 4 x + (8 x^{2} - 8) (x^{3} + x)}{{(x^{2} + 1)}^{4}}$

Step 2.5.3.1.11

Expand $(8 x^{2} - 8) (x^{3} + x)$ using the FOIL Method.

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Step 2.5.3.1.11.1

Apply the distributive property.

$f'' (x) = \frac{- 4 x^{5} - 8 x^{3} - 4 x + 8 x^{2} (x^{3} + x) - 8 (x^{3} + x)}{{(x^{2} + 1)}^{4}}$

Step 2.5.3.1.11.2

Apply the distributive property.

$f'' (x) = \frac{- 4 x^{5} - 8 x^{3} - 4 x + 8 x^{2} x^{3} + 8 x^{2} x - 8 (x^{3} + x)}{{(x^{2} + 1)}^{4}}$

Step 2.5.3.1.11.3

Apply the distributive property.

$f'' (x) = \frac{- 4 x^{5} - 8 x^{3} - 4 x + 8 x^{2} x^{3} + 8 x^{2} x - 8 x^{3} - 8 x}{{(x^{2} + 1)}^{4}}$

Step 2.5.3.1.12

Simplify and combine like terms.

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Step 2.5.3.1.12.1

Simplify each term.

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Step 2.5.3.1.12.1.1

Multiply $x^{2}$ by $x^{3}$ by adding the exponents.

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Step 2.5.3.1.12.1.1.1

Move $x^{3}$ .

$f'' (x) = \frac{- 4 x^{5} - 8 x^{3} - 4 x + 8 (x^{3} x^{2}) + 8 x^{2} x - 8 x^{3} - 8 x}{{(x^{2} + 1)}^{4}}$

Step 2.5.3.1.12.1.1.2

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

$f'' (x) = \frac{- 4 x^{5} - 8 x^{3} - 4 x + 8 x^{3 + 2} + 8 x^{2} x - 8 x^{3} - 8 x}{{(x^{2} + 1)}^{4}}$

Step 2.5.3.1.12.1.1.3

Add $3$ and $2$ .

$f'' (x) = \frac{- 4 x^{5} - 8 x^{3} - 4 x + 8 x^{5} + 8 x^{2} x - 8 x^{3} - 8 x}{{(x^{2} + 1)}^{4}}$

Step 2.5.3.1.12.1.2

Multiply $x^{2}$ by $x$ by adding the exponents.

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Step 2.5.3.1.12.1.2.1

Move $x$ .

$f'' (x) = \frac{- 4 x^{5} - 8 x^{3} - 4 x + 8 x^{5} + 8 (x \cdot x^{2}) - 8 x^{3} - 8 x}{{(x^{2} + 1)}^{4}}$

Step 2.5.3.1.12.1.2.2

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

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Step 2.5.3.1.12.1.2.2.1

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

$f'' (x) = \frac{- 4 x^{5} - 8 x^{3} - 4 x + 8 x^{5} + 8 (x \cdot x^{2}) - 8 x^{3} - 8 x}{{(x^{2} + 1)}^{4}}$

Step 2.5.3.1.12.1.2.2.2

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

$f'' (x) = \frac{- 4 x^{5} - 8 x^{3} - 4 x + 8 x^{5} + 8 x^{1 + 2} - 8 x^{3} - 8 x}{{(x^{2} + 1)}^{4}}$

Step 2.5.3.1.12.1.2.3

Add $1$ and $2$ .

$f'' (x) = \frac{- 4 x^{5} - 8 x^{3} - 4 x + 8 x^{5} + 8 x^{3} - 8 x^{3} - 8 x}{{(x^{2} + 1)}^{4}}$

Step 2.5.3.1.12.2

Subtract $8 x^{3}$ from $8 x^{3}$ .

$f'' (x) = \frac{- 4 x^{5} - 8 x^{3} - 4 x + 8 x^{5} + 0 - 8 x}{{(x^{2} + 1)}^{4}}$

Step 2.5.3.1.12.3

Add $8 x^{5}$ and $0$ .

$f'' (x) = \frac{- 4 x^{5} - 8 x^{3} - 4 x + 8 x^{5} - 8 x}{{(x^{2} + 1)}^{4}}$

Step 2.5.3.2

Add $- 4 x^{5}$ and $8 x^{5}$ .

$f'' (x) = \frac{4 x^{5} - 8 x^{3} - 4 x - 8 x}{{(x^{2} + 1)}^{4}}$

Step 2.5.3.3

Subtract $8 x$ from $- 4 x$ .

$f'' (x) = \frac{4 x^{5} - 8 x^{3} - 12 x}{{(x^{2} + 1)}^{4}}$

Step 2.5.4

Simplify the numerator.

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Step 2.5.4.1

Factor $4 x$ out of $4 x^{5} - 8 x^{3} - 12 x$ .

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Step 2.5.4.1.1

Factor $4 x$ out of $4 x^{5}$ .

$f'' (x) = \frac{4 x (x^{4}) - 8 x^{3} - 12 x}{{(x^{2} + 1)}^{4}}$

Step 2.5.4.1.2

Factor $4 x$ out of $- 8 x^{3}$ .

$f'' (x) = \frac{4 x (x^{4}) + 4 x (- 2 x^{2}) - 12 x}{{(x^{2} + 1)}^{4}}$

Step 2.5.4.1.3

Factor $4 x$ out of $- 12 x$ .

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

Step 2.5.4.1.4

Factor $4 x$ out of $4 x (x^{4}) + 4 x (- 2 x^{2})$ .

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

Step 2.5.4.1.5

Factor $4 x$ out of $4 x (x^{4} - 2 x^{2}) + 4 x (- 3)$ .

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

Step 2.5.4.2

Rewrite $x^{4}$ as ${(x^{2})}^{2}$ .

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

Step 2.5.4.3

Let $u = x^{2}$ . Substitute $u$ for all occurrences of $x^{2}$ .

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

Step 2.5.4.4

Factor $u^{2} - 2 u - 3$ using the AC method.

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Step 2.5.4.4.1

Consider the form $x^{2} + b x + c$ . Find a pair of integers whose product is $c$ and whose sum is $b$ . In this case, whose product is $- 3$ and whose sum is $- 2$ .

$- 3, 1$

Step 2.5.4.4.2

Write the factored form using these integers.

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

Step 2.5.4.5

Replace all occurrences of $u$ with $x^{2}$ .

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

Step 2.5.5

Cancel the common factor of $x^{2} + 1$ and ${(x^{2} + 1)}^{4}$ .

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Step 2.5.5.1

Factor $x^{2} + 1$ out of $4 x (x^{2} - 3) (x^{2} + 1)$ .

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

Step 2.5.5.2

Cancel the common factors.

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Step 2.5.5.2.1

Factor $x^{2} + 1$ out of ${(x^{2} + 1)}^{4}$ .

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

Step 2.5.5.2.2

Cancel the common factor.

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

Step 2.5.5.2.3

Rewrite the expression.

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

Step 3

The second derivative of $f (x)$ with respect to $x$ is $\frac{4 x (x^{2} - 3)}{{(x^{2} + 1)}^{3}}$ .

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