Calculus Examples

$\frac{21 \sqrt[3]{x}}{x^{2} - 8}$

Step 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 $f (x) = 21 \sqrt[3]{x}$ and $g (x) = x^{2} - 8$ .

$\frac{(x^{2} - 8) \frac{d}{d x} [21 \sqrt[3]{x}] - 1 \cdot 21 \sqrt[3]{x} \frac{d}{d x} [x^{2} - 8]}{{(x^{2} - 8)}^{2}}$

Step 2

Differentiate.

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Step 2.1

Use $\sqrt[n]{a^{x}} = a^{\frac{x}{n}}$ to rewrite $\sqrt[3]{x}$ as $x^{\frac{1}{3}}$ .

$\frac{(x^{2} - 8) \frac{d}{d x} [21 x^{\frac{1}{3}}] - 1 \cdot 21 \sqrt[3]{x} \frac{d}{d x} [x^{2} - 8]}{{(x^{2} - 8)}^{2}}$

Step 2.2

Since $21$ is constant with respect to $x$ , the derivative of $21 x^{\frac{1}{3}}$ with respect to $x$ is $21 \frac{d}{d x} [x^{\frac{1}{3}}]$ .

$\frac{(x^{2} - 8) (21 \frac{d}{d x} [x^{\frac{1}{3}}]) - 1 \cdot 21 \sqrt[3]{x} \frac{d}{d x} [x^{2} - 8]}{{(x^{2} - 8)}^{2}}$

Step 2.3

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

$\frac{(x^{2} - 8) (21 (\frac{1}{3} x^{\frac{1}{3} - 1})) - 1 \cdot 21 \sqrt[3]{x} \frac{d}{d x} [x^{2} - 8]}{{(x^{2} - 8)}^{2}}$

Step 3

To write $- 1$ as a fraction with a common denominator, multiply by $\frac{3}{3}$ .

$\frac{(x^{2} - 8) (21 (\frac{1}{3} x^{\frac{1}{3} - 1 \cdot \frac{3}{3}})) - 1 \cdot 21 \sqrt[3]{x} \frac{d}{d x} [x^{2} - 8]}{{(x^{2} - 8)}^{2}}$

Step 4

Combine $- 1$ and $\frac{3}{3}$ .

$\frac{(x^{2} - 8) (21 (\frac{1}{3} x^{\frac{1}{3} + \frac{- 1 \cdot 3}{3}})) - 1 \cdot 21 \sqrt[3]{x} \frac{d}{d x} [x^{2} - 8]}{{(x^{2} - 8)}^{2}}$

Step 5

Combine the numerators over the common denominator.

$\frac{(x^{2} - 8) (21 (\frac{1}{3} x^{\frac{1 - 1 \cdot 3}{3}})) - 1 \cdot 21 \sqrt[3]{x} \frac{d}{d x} [x^{2} - 8]}{{(x^{2} - 8)}^{2}}$

Step 6

Simplify the numerator.

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Step 6.1

Multiply $- 1$ by $3$ .

$\frac{(x^{2} - 8) (21 (\frac{1}{3} x^{\frac{1 - 3}{3}})) - 1 \cdot 21 \sqrt[3]{x} \frac{d}{d x} [x^{2} - 8]}{{(x^{2} - 8)}^{2}}$

Step 6.2

Subtract $3$ from $1$ .

$\frac{(x^{2} - 8) (21 (\frac{1}{3} x^{\frac{- 2}{3}})) - 1 \cdot 21 \sqrt[3]{x} \frac{d}{d x} [x^{2} - 8]}{{(x^{2} - 8)}^{2}}$

Step 7

Move the negative in front of the fraction.

$\frac{(x^{2} - 8) (21 (\frac{1}{3} x^{- \frac{2}{3}})) - 1 \cdot 21 \sqrt[3]{x} \frac{d}{d x} [x^{2} - 8]}{{(x^{2} - 8)}^{2}}$

Step 8

Combine $\frac{1}{3}$ and $x^{- \frac{2}{3}}$ .

$\frac{(x^{2} - 8) (21 \frac{x^{- \frac{2}{3}}}{3}) - 1 \cdot 21 \sqrt[3]{x} \frac{d}{d x} [x^{2} - 8]}{{(x^{2} - 8)}^{2}}$

Step 9

Combine $21$ and $\frac{x^{- \frac{2}{3}}}{3}$ .

$\frac{(x^{2} - 8) \frac{21 x^{- \frac{2}{3}}}{3} - 1 \cdot 21 \sqrt[3]{x} \frac{d}{d x} [x^{2} - 8]}{{(x^{2} - 8)}^{2}}$

Step 10

Move $x^{- \frac{2}{3}}$ to the denominator using the negative exponent rule $b^{- n} = \frac{1}{b^{n}}$ .

$\frac{(x^{2} - 8) \frac{21}{3 x^{\frac{2}{3}}} - 1 \cdot 21 \sqrt[3]{x} \frac{d}{d x} [x^{2} - 8]}{{(x^{2} - 8)}^{2}}$

Step 11

Factor $3$ out of $21$ .

$\frac{(x^{2} - 8) \frac{3 \cdot 7}{3 x^{\frac{2}{3}}} - 1 \cdot 21 \sqrt[3]{x} \frac{d}{d x} [x^{2} - 8]}{{(x^{2} - 8)}^{2}}$

Step 12

Cancel the common factors.

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Step 12.1

Factor $3$ out of $3 x^{\frac{2}{3}}$ .

$\frac{(x^{2} - 8) \frac{3 \cdot 7}{3 (x^{\frac{2}{3}})} - 1 \cdot 21 \sqrt[3]{x} \frac{d}{d x} [x^{2} - 8]}{{(x^{2} - 8)}^{2}}$

Step 12.2

Cancel the common factor.

$\frac{(x^{2} - 8) \frac{3 \cdot 7}{3 x^{\frac{2}{3}}} - 1 \cdot 21 \sqrt[3]{x} \frac{d}{d x} [x^{2} - 8]}{{(x^{2} - 8)}^{2}}$

Step 12.3

Rewrite the expression.

$\frac{(x^{2} - 8) \frac{7}{x^{\frac{2}{3}}} - 1 \cdot 21 \sqrt[3]{x} \frac{d}{d x} [x^{2} - 8]}{{(x^{2} - 8)}^{2}}$

Step 13

By the Sum Rule, the derivative of $x^{2} - 8$ with respect to $x$ is $\frac{d}{d x} [x^{2}] + \frac{d}{d x} [- 8]$ .

$\frac{(x^{2} - 8) \frac{7}{x^{\frac{2}{3}}} - 1 \cdot 21 \sqrt[3]{x} (\frac{d}{d x} [x^{2}] + \frac{d}{d x} [- 8])}{{(x^{2} - 8)}^{2}}$

Step 14

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

$\frac{(x^{2} - 8) \frac{7}{x^{\frac{2}{3}}} - 1 \cdot 21 \sqrt[3]{x} (2 x + \frac{d}{d x} [- 8])}{{(x^{2} - 8)}^{2}}$

Step 15

Since $- 8$ is constant with respect to $x$ , the derivative of $- 8$ with respect to $x$ is $0$ .

$\frac{(x^{2} - 8) \frac{7}{x^{\frac{2}{3}}} - 1 \cdot 21 \sqrt[3]{x} (2 x + 0)}{{(x^{2} - 8)}^{2}}$

Step 16

Add $2 x$ and $0$ .

$\frac{(x^{2} - 8) \frac{7}{x^{\frac{2}{3}}} - 1 \cdot 21 \sqrt[3]{x} (2 x)}{{(x^{2} - 8)}^{2}}$

Step 17

Simplify.

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Step 17.1

Apply the distributive property.

$\frac{x^{2} \frac{7}{x^{\frac{2}{3}}} - 8 \frac{7}{x^{\frac{2}{3}}} - 1 \cdot 21 \sqrt[3]{x} (2 x)}{{(x^{2} - 8)}^{2}}$

Step 17.2

Simplify each term.

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Step 17.2.1

Cancel the common factor of $x^{\frac{2}{3}}$ .

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Step 17.2.1.1

Factor $x^{\frac{2}{3}}$ out of $x^{2}$ .

$\frac{x^{\frac{2}{3}} x^{\frac{4}{3}} \frac{7}{x^{\frac{2}{3}}} - 8 \frac{7}{x^{\frac{2}{3}}} - 1 \cdot 21 \sqrt[3]{x} (2 x)}{{(x^{2} - 8)}^{2}}$

Step 17.2.1.2

Cancel the common factor.

$\frac{x^{\frac{2}{3}} x^{\frac{4}{3}} \frac{7}{x^{\frac{2}{3}}} - 8 \frac{7}{x^{\frac{2}{3}}} - 1 \cdot 21 \sqrt[3]{x} (2 x)}{{(x^{2} - 8)}^{2}}$

Step 17.2.1.3

Rewrite the expression.

$\frac{x^{\frac{4}{3}} \cdot 7 - 8 \frac{7}{x^{\frac{2}{3}}} - 1 \cdot 21 \sqrt[3]{x} (2 x)}{{(x^{2} - 8)}^{2}}$

Step 17.2.2

Move $7$ to the left of $x^{\frac{4}{3}}$ .

$\frac{7 \cdot x^{\frac{4}{3}} - 8 \frac{7}{x^{\frac{2}{3}}} - 1 \cdot 21 \sqrt[3]{x} (2 x)}{{(x^{2} - 8)}^{2}}$

Step 17.2.3

Multiply $- 8 \frac{7}{x^{\frac{2}{3}}}$ .

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Step 17.2.3.1

Combine $- 8$ and $\frac{7}{x^{\frac{2}{3}}}$ .

$\frac{7 x^{\frac{4}{3}} + \frac{- 8 \cdot 7}{x^{\frac{2}{3}}} - 1 \cdot 21 \sqrt[3]{x} (2 x)}{{(x^{2} - 8)}^{2}}$

Step 17.2.3.2

Multiply $- 8$ by $7$ .

$\frac{7 x^{\frac{4}{3}} + \frac{- 56}{x^{\frac{2}{3}}} - 1 \cdot 21 \sqrt[3]{x} (2 x)}{{(x^{2} - 8)}^{2}}$

Step 17.2.4

Move the negative in front of the fraction.

$\frac{7 x^{\frac{4}{3}} - \frac{56}{x^{\frac{2}{3}}} - 1 \cdot 21 \sqrt[3]{x} (2 x)}{{(x^{2} - 8)}^{2}}$

Step 17.2.5

Multiply $- 1$ by $21$ .

$\frac{7 x^{\frac{4}{3}} - \frac{56}{x^{\frac{2}{3}}} - 21 \sqrt[3]{x} (2 x)}{{(x^{2} - 8)}^{2}}$

Step 17.2.6

Multiply $2$ by $- 21$ .

$\frac{7 x^{\frac{4}{3}} - \frac{56}{x^{\frac{2}{3}}} - 42 \sqrt[3]{x} x}{{(x^{2} - 8)}^{2}}$

Step 17.3

Combine terms.

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Step 17.3.1

Use $\sqrt[n]{a^{x}} = a^{\frac{x}{n}}$ to rewrite $\sqrt[3]{x}$ as $x^{\frac{1}{3}}$ .

$\frac{7 x^{\frac{4}{3}} - \frac{56}{x^{\frac{2}{3}}} - 42 x^{\frac{1}{3}} x}{{(x^{2} - 8)}^{2}}$

Step 17.3.2

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

$\frac{7 x^{\frac{4}{3}} - \frac{56}{x^{\frac{2}{3}}} - 42 (x^{1} x^{\frac{1}{3}})}{{(x^{2} - 8)}^{2}}$

Step 17.3.3

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

$\frac{7 x^{\frac{4}{3}} - \frac{56}{x^{\frac{2}{3}}} - 42 x^{1 + \frac{1}{3}}}{{(x^{2} - 8)}^{2}}$

Step 17.3.4

Write $1$ as a fraction with a common denominator.

$\frac{7 x^{\frac{4}{3}} - \frac{56}{x^{\frac{2}{3}}} - 42 x^{\frac{3}{3} + \frac{1}{3}}}{{(x^{2} - 8)}^{2}}$

Step 17.3.5

Combine the numerators over the common denominator.

$\frac{7 x^{\frac{4}{3}} - \frac{56}{x^{\frac{2}{3}}} - 42 x^{\frac{3 + 1}{3}}}{{(x^{2} - 8)}^{2}}$

Step 17.3.6

Add $3$ and $1$ .

$\frac{7 x^{\frac{4}{3}} - \frac{56}{x^{\frac{2}{3}}} - 42 x^{\frac{4}{3}}}{{(x^{2} - 8)}^{2}}$

Step 17.3.7

Subtract $42 x^{\frac{4}{3}}$ from $7 x^{\frac{4}{3}}$ .

$\frac{- 35 x^{\frac{4}{3}} - \frac{56}{x^{\frac{2}{3}}}}{{(x^{2} - 8)}^{2}}$

Step 17.4

Simplify the numerator.

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Step 17.4.1

Factor $- 7$ out of $- 35 x^{\frac{4}{3}} - \frac{56}{x^{\frac{2}{3}}}$ .

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Step 17.4.1.1

Factor $- 7$ out of $- 35 x^{\frac{4}{3}}$ .

$\frac{- 7 (5 x^{\frac{4}{3}}) - \frac{56}{x^{\frac{2}{3}}}}{{(x^{2} - 8)}^{2}}$

Step 17.4.1.2

Factor $- 7$ out of $- \frac{56}{x^{\frac{2}{3}}}$ .

$\frac{- 7 (5 x^{\frac{4}{3}}) - 7 (- \frac{- 8}{x^{\frac{2}{3}}})}{{(x^{2} - 8)}^{2}}$

Step 17.4.1.3

Factor $- 7$ out of $- 7 (5 x^{\frac{4}{3}}) - 7 (- \frac{- 8}{x^{\frac{2}{3}}})$ .

$\frac{- 7 (5 x^{\frac{4}{3}} - \frac{- 8}{x^{\frac{2}{3}}})}{{(x^{2} - 8)}^{2}}$

Step 17.4.2

Move the negative in front of the fraction.

$\frac{- 7 (5 x^{\frac{4}{3}} - - \frac{8}{x^{\frac{2}{3}}})}{{(x^{2} - 8)}^{2}}$

Step 17.4.3

Multiply $- - \frac{8}{x^{\frac{2}{3}}}$ .

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Step 17.4.3.1

Multiply $- 1$ by $- 1$ .

$\frac{- 7 (5 x^{\frac{4}{3}} + 1 \frac{8}{x^{\frac{2}{3}}})}{{(x^{2} - 8)}^{2}}$

Step 17.4.3.2

Multiply $\frac{8}{x^{\frac{2}{3}}}$ by $1$ .

$\frac{- 7 (5 x^{\frac{4}{3}} + \frac{8}{x^{\frac{2}{3}}})}{{(x^{2} - 8)}^{2}}$

Step 17.4.4

To write $5 x^{\frac{4}{3}}$ as a fraction with a common denominator, multiply by $\frac{x^{\frac{2}{3}}}{x^{\frac{2}{3}}}$ .

$\frac{- 7 (\frac{5 x^{\frac{4}{3}} x^{\frac{2}{3}}}{x^{\frac{2}{3}}} + \frac{8}{x^{\frac{2}{3}}})}{{(x^{2} - 8)}^{2}}$

Step 17.4.5

Combine the numerators over the common denominator.

$\frac{- 7 \frac{5 x^{\frac{4}{3}} x^{\frac{2}{3}} + 8}{x^{\frac{2}{3}}}}{{(x^{2} - 8)}^{2}}$

Step 17.4.6

Multiply $x^{\frac{4}{3}}$ by $x^{\frac{2}{3}}$ by adding the exponents.

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Step 17.4.6.1

Move $x^{\frac{2}{3}}$ .

$\frac{- 7 \frac{5 (x^{\frac{2}{3}} x^{\frac{4}{3}}) + 8}{x^{\frac{2}{3}}}}{{(x^{2} - 8)}^{2}}$

Step 17.4.6.2

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

$\frac{- 7 \frac{5 x^{\frac{2}{3} + \frac{4}{3}} + 8}{x^{\frac{2}{3}}}}{{(x^{2} - 8)}^{2}}$

Step 17.4.6.3

Combine the numerators over the common denominator.

$\frac{- 7 \frac{5 x^{\frac{2 + 4}{3}} + 8}{x^{\frac{2}{3}}}}{{(x^{2} - 8)}^{2}}$

Step 17.4.6.4

Add $2$ and $4$ .

$\frac{- 7 \frac{5 x^{\frac{6}{3}} + 8}{x^{\frac{2}{3}}}}{{(x^{2} - 8)}^{2}}$

Step 17.4.6.5

Divide $6$ by $3$ .

$\frac{- 7 \frac{5 x^{2} + 8}{x^{\frac{2}{3}}}}{{(x^{2} - 8)}^{2}}$

Step 17.5

Combine $- 7$ and $\frac{5 x^{2} + 8}{x^{\frac{2}{3}}}$ .

$\frac{\frac{- 7 (5 x^{2} + 8)}{x^{\frac{2}{3}}}}{{(x^{2} - 8)}^{2}}$

Step 17.6

Move the negative in front of the fraction.

$\frac{- \frac{7 (5 x^{2} + 8)}{x^{\frac{2}{3}}}}{{(x^{2} - 8)}^{2}}$

Step 17.7

Multiply the numerator by the reciprocal of the denominator.

$- \frac{7 (5 x^{2} + 8)}{x^{\frac{2}{3}}} \cdot \frac{1}{{(x^{2} - 8)}^{2}}$

Step 17.8

Multiply $\frac{1}{{(x^{2} - 8)}^{2}}$ by $\frac{7 (5 x^{2} + 8)}{x^{\frac{2}{3}}}$ .

$- \frac{7 (5 x^{2} + 8)}{{(x^{2} - 8)}^{2} x^{\frac{2}{3}}}$

Step 17.9

Reorder factors in $- \frac{7 (5 x^{2} + 8)}{{(x^{2} - 8)}^{2} x^{\frac{2}{3}}}$ .

$- \frac{7 (5 x^{2} + 8)}{x^{\frac{2}{3}} {(x^{2} - 8)}^{2}}$