Calculus Examples

$f (x) = {(3 x^{4} - 8 x)}^{3} + \sqrt{x}$

Step 1

By the Sum Rule, the derivative of ${(3 x^{4} - 8 x)}^{3} + \sqrt{x}$ with respect to $x$ is $\frac{d}{d x} [{(3 x^{4} - 8 x)}^{3}] + \frac{d}{d x} [\sqrt{x}]$ .

$\frac{d}{d x} [{(3 x^{4} - 8 x)}^{3}] + \frac{d}{d x} [\sqrt{x}]$

Step 2

Evaluate $\frac{d}{d x} [{(3 x^{4} - 8 x)}^{3}]$ .

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Step 2.1

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = x^{3}$ and $g (x) = 3 x^{4} - 8 x$ .

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Step 2.1.1

To apply the Chain Rule, set $u$ as $3 x^{4} - 8 x$ .

$\frac{d}{d u} [u^{3}] \frac{d}{d x} [3 x^{4} - 8 x] + \frac{d}{d x} [\sqrt{x}]$

Step 2.1.2

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

$3 u^{2} \frac{d}{d x} [3 x^{4} - 8 x] + \frac{d}{d x} [\sqrt{x}]$

Step 2.1.3

Replace all occurrences of $u$ with $3 x^{4} - 8 x$ .

$3 {(3 x^{4} - 8 x)}^{2} \frac{d}{d x} [3 x^{4} - 8 x] + \frac{d}{d x} [\sqrt{x}]$

Step 2.2

By the Sum Rule, the derivative of $3 x^{4} - 8 x$ with respect to $x$ is $\frac{d}{d x} [3 x^{4}] + \frac{d}{d x} [- 8 x]$ .

$3 {(3 x^{4} - 8 x)}^{2} (\frac{d}{d x} [3 x^{4}] + \frac{d}{d x} [- 8 x]) + \frac{d}{d x} [\sqrt{x}]$

Step 2.3

Since $3$ is constant with respect to $x$ , the derivative of $3 x^{4}$ with respect to $x$ is $3 \frac{d}{d x} [x^{4}]$ .

$3 {(3 x^{4} - 8 x)}^{2} (3 \frac{d}{d x} [x^{4}] + \frac{d}{d x} [- 8 x]) + \frac{d}{d x} [\sqrt{x}]$

Step 2.4

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 4$ .

$3 {(3 x^{4} - 8 x)}^{2} (3 (4 x^{3}) + \frac{d}{d x} [- 8 x]) + \frac{d}{d x} [\sqrt{x}]$

Step 2.5

Since $- 8$ is constant with respect to $x$ , the derivative of $- 8 x$ with respect to $x$ is $- 8 \frac{d}{d x} [x]$ .

$3 {(3 x^{4} - 8 x)}^{2} (3 (4 x^{3}) - 8 \frac{d}{d x} [x]) + \frac{d}{d x} [\sqrt{x}]$

Step 2.6

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

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

Step 2.7

Multiply $4$ by $3$ .

$3 {(3 x^{4} - 8 x)}^{2} (12 x^{3} - 8 \cdot 1) + \frac{d}{d x} [\sqrt{x}]$

Step 2.8

Multiply $- 8$ by $1$ .

$3 {(3 x^{4} - 8 x)}^{2} (12 x^{3} - 8) + \frac{d}{d x} [\sqrt{x}]$

Step 3

Evaluate $\frac{d}{d x} [\sqrt{x}]$ .

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Step 3.1

Use $\sqrt[n]{a^{x}} = a^{\frac{x}{n}}$ to rewrite $\sqrt{x}$ as $x^{\frac{1}{2}}$ .

$3 {(3 x^{4} - 8 x)}^{2} (12 x^{3} - 8) + \frac{d}{d x} [x^{\frac{1}{2}}]$

Step 3.2

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

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

Step 3.3

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

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

Step 3.4

Combine $- 1$ and $\frac{2}{2}$ .

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

Step 3.5

Combine the numerators over the common denominator.

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

Step 3.6

Simplify the numerator.

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Step 3.6.1

Multiply $- 1$ by $2$ .

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

Step 3.6.2

Subtract $2$ from $1$ .

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

Step 3.7

Move the negative in front of the fraction.

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

Step 4

Rewrite the expression using the negative exponent rule $b^{- n} = \frac{1}{b^{n}}$ .

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

Step 5

Simplify.

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Step 5.1

Combine terms.

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Step 5.1.1

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

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

Step 5.1.2

To write $3 {(3 x^{4} - 8 x)}^{2} (12 x^{3} - 8)$ as a fraction with a common denominator, multiply by $\frac{2 x^{\frac{1}{2}}}{2 x^{\frac{1}{2}}}$ .

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

Step 5.1.3

Combine $3 {(3 x^{4} - 8 x)}^{2} (12 x^{3} - 8)$ and $\frac{2 x^{\frac{1}{2}}}{2 x^{\frac{1}{2}}}$ .

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

Step 5.1.4

Combine the numerators over the common denominator.

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

Step 5.1.5

Multiply $2$ by $3$ .

$\frac{6 {(3 x^{4} - 8 x)}^{2} (12 x^{3} - 8) x^{\frac{1}{2}} + 1}{2 x^{\frac{1}{2}}}$

Step 5.2

Reorder terms.

$\frac{6 x^{\frac{1}{2}} {(3 x^{4} - 8 x)}^{2} (12 x^{3} - 8) + 1}{2 x^{\frac{1}{2}}}$