Calculus Examples

$f = (- 6 r^{9} - 1 - \frac{9}{r^{2}}) (4 r^{4} - 7)$

Step 1

Differentiate both sides of the equation.

$\frac{d}{d r} (f) = \frac{d}{d r} ((- 6 r^{9} - 1 - \frac{9}{r^{2}}) (4 r^{4} - 7))$

Step 2

The derivative of $f$ with respect to $r$ is $f'$ .

$f'$

Step 3

Differentiate the right side of the equation.

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Step 3.1

Differentiate using the Product Rule which states that $\frac{d}{d r} [f (r) g (r)]$ is $f (r) \frac{d}{d r} [g (r)] + g (r) \frac{d}{d r} [f (r)]$ where $f (r) = - 6 r^{9} - 1 - \frac{9}{r^{2}}$ and $g (r) = 4 r^{4} - 7$ .

$(- 6 r^{9} - 1 - \frac{9}{r^{2}}) \frac{d}{d r} [4 r^{4} - 7] + (4 r^{4} - 7) \frac{d}{d r} [- 6 r^{9} - 1 - \frac{9}{r^{2}}]$

Step 3.2

Differentiate.

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Step 3.2.1

By the Sum Rule, the derivative of $4 r^{4} - 7$ with respect to $r$ is $\frac{d}{d r} [4 r^{4}] + \frac{d}{d r} [- 7]$ .

$(- 6 r^{9} - 1 - \frac{9}{r^{2}}) (\frac{d}{d r} [4 r^{4}] + \frac{d}{d r} [- 7]) + (4 r^{4} - 7) \frac{d}{d r} [- 6 r^{9} - 1 - \frac{9}{r^{2}}]$

Step 3.2.2

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

$(- 6 r^{9} - 1 - \frac{9}{r^{2}}) (4 \frac{d}{d r} [r^{4}] + \frac{d}{d r} [- 7]) + (4 r^{4} - 7) \frac{d}{d r} [- 6 r^{9} - 1 - \frac{9}{r^{2}}]$

Step 3.2.3

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

$(- 6 r^{9} - 1 - \frac{9}{r^{2}}) (4 (4 r^{3}) + \frac{d}{d r} [- 7]) + (4 r^{4} - 7) \frac{d}{d r} [- 6 r^{9} - 1 - \frac{9}{r^{2}}]$

Step 3.2.4

Multiply $4$ by $4$ .

$(- 6 r^{9} - 1 - \frac{9}{r^{2}}) (16 r^{3} + \frac{d}{d r} [- 7]) + (4 r^{4} - 7) \frac{d}{d r} [- 6 r^{9} - 1 - \frac{9}{r^{2}}]$

Step 3.2.5

Since $- 7$ is constant with respect to $r$ , the derivative of $- 7$ with respect to $r$ is $0$ .

$(- 6 r^{9} - 1 - \frac{9}{r^{2}}) (16 r^{3} + 0) + (4 r^{4} - 7) \frac{d}{d r} [- 6 r^{9} - 1 - \frac{9}{r^{2}}]$

Step 3.2.6

Simplify the expression.

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Step 3.2.6.1

Add $16 r^{3}$ and $0$ .

$(- 6 r^{9} - 1 - \frac{9}{r^{2}}) (16 r^{3}) + (4 r^{4} - 7) \frac{d}{d r} [- 6 r^{9} - 1 - \frac{9}{r^{2}}]$

Step 3.2.6.2

Move $16$ to the left of $- 6 r^{9} - 1 - \frac{9}{r^{2}}$ .

$16 \cdot (- 6 r^{9} - 1 - \frac{9}{r^{2}}) r^{3} + (4 r^{4} - 7) \frac{d}{d r} [- 6 r^{9} - 1 - \frac{9}{r^{2}}]$

Step 3.2.7

By the Sum Rule, the derivative of $- 6 r^{9} - 1 - \frac{9}{r^{2}}$ with respect to $r$ is $\frac{d}{d r} [- 6 r^{9}] + \frac{d}{d r} [- 1] + \frac{d}{d r} [- \frac{9}{r^{2}}]$ .

$16 (- 6 r^{9} - 1 - \frac{9}{r^{2}}) r^{3} + (4 r^{4} - 7) (\frac{d}{d r} [- 6 r^{9}] + \frac{d}{d r} [- 1] + \frac{d}{d r} [- \frac{9}{r^{2}}])$

Step 3.2.8

Since $- 6$ is constant with respect to $r$ , the derivative of $- 6 r^{9}$ with respect to $r$ is $- 6 \frac{d}{d r} [r^{9}]$ .

$16 (- 6 r^{9} - 1 - \frac{9}{r^{2}}) r^{3} + (4 r^{4} - 7) (- 6 \frac{d}{d r} [r^{9}] + \frac{d}{d r} [- 1] + \frac{d}{d r} [- \frac{9}{r^{2}}])$

Step 3.2.9

Differentiate using the Power Rule which states that $\frac{d}{d r} [r^{n}]$ is $n r^{n - 1}$ where $n = 9$ .

$16 (- 6 r^{9} - 1 - \frac{9}{r^{2}}) r^{3} + (4 r^{4} - 7) (- 6 (9 r^{8}) + \frac{d}{d r} [- 1] + \frac{d}{d r} [- \frac{9}{r^{2}}])$

Step 3.2.10

Multiply $9$ by $- 6$ .

$16 (- 6 r^{9} - 1 - \frac{9}{r^{2}}) r^{3} + (4 r^{4} - 7) (- 54 r^{8} + \frac{d}{d r} [- 1] + \frac{d}{d r} [- \frac{9}{r^{2}}])$

Step 3.2.11

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

$16 (- 6 r^{9} - 1 - \frac{9}{r^{2}}) r^{3} + (4 r^{4} - 7) (- 54 r^{8} + 0 + \frac{d}{d r} [- \frac{9}{r^{2}}])$

Step 3.2.12

Add $- 54 r^{8}$ and $0$ .

$16 (- 6 r^{9} - 1 - \frac{9}{r^{2}}) r^{3} + (4 r^{4} - 7) (- 54 r^{8} + \frac{d}{d r} [- \frac{9}{r^{2}}])$

Step 3.2.13

Since $- 9$ is constant with respect to $r$ , the derivative of $- \frac{9}{r^{2}}$ with respect to $r$ is $- 9 \frac{d}{d r} [\frac{1}{r^{2}}]$ .

$16 (- 6 r^{9} - 1 - \frac{9}{r^{2}}) r^{3} + (4 r^{4} - 7) (- 54 r^{8} - 9 \frac{d}{d r} [\frac{1}{r^{2}}])$

Step 3.2.14

Apply basic rules of exponents.

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Step 3.2.14.1

Rewrite $\frac{1}{r^{2}}$ as ${(r^{2})}^{- 1}$ .

$16 (- 6 r^{9} - 1 - \frac{9}{r^{2}}) r^{3} + (4 r^{4} - 7) (- 54 r^{8} - 9 \frac{d}{d r} [{(r^{2})}^{- 1}])$

Step 3.2.14.2

Multiply the exponents in ${(r^{2})}^{- 1}$ .

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Step 3.2.14.2.1

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

$16 (- 6 r^{9} - 1 - \frac{9}{r^{2}}) r^{3} + (4 r^{4} - 7) (- 54 r^{8} - 9 \frac{d}{d r} [r^{2 \cdot - 1}])$

Step 3.2.14.2.2

Multiply $2$ by $- 1$ .

$16 (- 6 r^{9} - 1 - \frac{9}{r^{2}}) r^{3} + (4 r^{4} - 7) (- 54 r^{8} - 9 \frac{d}{d r} [r^{- 2}])$

Step 3.2.15

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

$16 (- 6 r^{9} - 1 - \frac{9}{r^{2}}) r^{3} + (4 r^{4} - 7) (- 54 r^{8} - 9 (- 2 r^{- 3}))$

Step 3.2.16

Multiply $- 2$ by $- 9$ .

$16 (- 6 r^{9} - 1 - \frac{9}{r^{2}}) r^{3} + (4 r^{4} - 7) (- 54 r^{8} + 18 r^{- 3})$

Step 3.3

Simplify.

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Step 3.3.1

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

$16 (- 6 r^{9} - 1 - \frac{9}{r^{2}}) r^{3} + (4 r^{4} - 7) (- 54 r^{8} + 18 \frac{1}{r^{3}})$

Step 3.3.2

Apply the distributive property.

$(16 (- 6 r^{9}) + 16 \cdot - 1 + 16 (- \frac{9}{r^{2}})) r^{3} + (4 r^{4} - 7) (- 54 r^{8} + 18 \frac{1}{r^{3}})$

Step 3.3.3

Apply the distributive property.

$16 (- 6 r^{9}) r^{3} + 16 \cdot - 1 r^{3} + 16 (- \frac{9}{r^{2}}) r^{3} + (4 r^{4} - 7) (- 54 r^{8} + 18 \frac{1}{r^{3}})$

Step 3.3.4

Combine terms.

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Step 3.3.4.1

Multiply $- 6$ by $16$ .

$- 96 r^{9} r^{3} + 16 \cdot - 1 r^{3} + 16 (- \frac{9}{r^{2}}) r^{3} + (4 r^{4} - 7) (- 54 r^{8} + 18 \frac{1}{r^{3}})$

Step 3.3.4.2

Multiply $r^{9}$ by $r^{3}$ by adding the exponents.

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Step 3.3.4.2.1

Move $r^{3}$ .

$- 96 (r^{3} r^{9}) + 16 \cdot - 1 r^{3} + 16 (- \frac{9}{r^{2}}) r^{3} + (4 r^{4} - 7) (- 54 r^{8} + 18 \frac{1}{r^{3}})$

Step 3.3.4.2.2

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

$- 96 r^{3 + 9} + 16 \cdot - 1 r^{3} + 16 (- \frac{9}{r^{2}}) r^{3} + (4 r^{4} - 7) (- 54 r^{8} + 18 \frac{1}{r^{3}})$

Step 3.3.4.2.3

Add $3$ and $9$ .

$- 96 r^{12} + 16 \cdot - 1 r^{3} + 16 (- \frac{9}{r^{2}}) r^{3} + (4 r^{4} - 7) (- 54 r^{8} + 18 \frac{1}{r^{3}})$

Step 3.3.4.3

Multiply $16$ by $- 1$ .

$- 96 r^{12} - 16 r^{3} + 16 (- \frac{9}{r^{2}}) r^{3} + (4 r^{4} - 7) (- 54 r^{8} + 18 \frac{1}{r^{3}})$

Step 3.3.4.4

Multiply $- 1$ by $16$ .

$- 96 r^{12} - 16 r^{3} - 16 \frac{9}{r^{2}} r^{3} + (4 r^{4} - 7) (- 54 r^{8} + 18 \frac{1}{r^{3}})$

Step 3.3.4.5

Combine $- 16$ and $\frac{9}{r^{2}}$ .

$- 96 r^{12} - 16 r^{3} + \frac{- 16 \cdot 9}{r^{2}} r^{3} + (4 r^{4} - 7) (- 54 r^{8} + 18 \frac{1}{r^{3}})$

Step 3.3.4.6

Multiply $- 16$ by $9$ .

$- 96 r^{12} - 16 r^{3} + \frac{- 144}{r^{2}} r^{3} + (4 r^{4} - 7) (- 54 r^{8} + 18 \frac{1}{r^{3}})$

Step 3.3.4.7

Move the negative in front of the fraction.

$- 96 r^{12} - 16 r^{3} - \frac{144}{r^{2}} r^{3} + (4 r^{4} - 7) (- 54 r^{8} + 18 \frac{1}{r^{3}})$

Step 3.3.4.8

Combine $r^{3}$ and $\frac{144}{r^{2}}$ .

$- 96 r^{12} - 16 r^{3} - \frac{r^{3} \cdot 144}{r^{2}} + (4 r^{4} - 7) (- 54 r^{8} + 18 \frac{1}{r^{3}})$

Step 3.3.4.9

Move $144$ to the left of $r^{3}$ .

$- 96 r^{12} - 16 r^{3} - \frac{144 \cdot r^{3}}{r^{2}} + (4 r^{4} - 7) (- 54 r^{8} + 18 \frac{1}{r^{3}})$

Step 3.3.4.10

Cancel the common factor of $r^{3}$ and $r^{2}$ .

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Step 3.3.4.10.1

Factor $r^{2}$ out of $144 r^{3}$ .

$- 96 r^{12} - 16 r^{3} - \frac{r^{2} (144 r)}{r^{2}} + (4 r^{4} - 7) (- 54 r^{8} + 18 \frac{1}{r^{3}})$

Step 3.3.4.10.2

Cancel the common factors.

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Step 3.3.4.10.2.1

Multiply by $1$ .

$- 96 r^{12} - 16 r^{3} - \frac{r^{2} (144 r)}{r^{2} \cdot 1} + (4 r^{4} - 7) (- 54 r^{8} + 18 \frac{1}{r^{3}})$

Step 3.3.4.10.2.2

Cancel the common factor.

$- 96 r^{12} - 16 r^{3} - \frac{r^{2} (144 r)}{r^{2} \cdot 1} + (4 r^{4} - 7) (- 54 r^{8} + 18 \frac{1}{r^{3}})$

Step 3.3.4.10.2.3

Rewrite the expression.

$- 96 r^{12} - 16 r^{3} - \frac{144 r}{1} + (4 r^{4} - 7) (- 54 r^{8} + 18 \frac{1}{r^{3}})$

Step 3.3.4.10.2.4

Divide $144 r$ by $1$ .

$- 96 r^{12} - 16 r^{3} - (144 r) + (4 r^{4} - 7) (- 54 r^{8} + 18 \frac{1}{r^{3}})$

Step 3.3.4.11

Multiply $144$ by $- 1$ .

$- 96 r^{12} - 16 r^{3} - 144 r + (4 r^{4} - 7) (- 54 r^{8} + 18 \frac{1}{r^{3}})$

Step 3.3.4.12

Combine $18$ and $\frac{1}{r^{3}}$ .

$- 96 r^{12} - 16 r^{3} - 144 r + (4 r^{4} - 7) (- 54 r^{8} + \frac{18}{r^{3}})$

Step 3.3.5

Reorder terms.

$- 96 r^{12} - 16 r^{3} + (- 54 r^{8} + \frac{18}{r^{3}}) (4 r^{4} - 7) - 144 r$

Step 3.3.6

Simplify each term.

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Step 3.3.6.1

Expand $(- 54 r^{8} + \frac{18}{r^{3}}) (4 r^{4} - 7)$ using the FOIL Method.

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Step 3.3.6.1.1

Apply the distributive property.

$- 96 r^{12} - 16 r^{3} - 54 r^{8} (4 r^{4} - 7) + \frac{18}{r^{3}} (4 r^{4} - 7) - 144 r$

Step 3.3.6.1.2

Apply the distributive property.

$- 96 r^{12} - 16 r^{3} - 54 r^{8} (4 r^{4}) - 54 r^{8} \cdot - 7 + \frac{18}{r^{3}} (4 r^{4} - 7) - 144 r$

Step 3.3.6.1.3

Apply the distributive property.

$- 96 r^{12} - 16 r^{3} - 54 r^{8} (4 r^{4}) - 54 r^{8} \cdot - 7 + \frac{18}{r^{3}} (4 r^{4}) + \frac{18}{r^{3}} \cdot - 7 - 144 r$

Step 3.3.6.2

Simplify each term.

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Step 3.3.6.2.1

Rewrite using the commutative property of multiplication.

$- 96 r^{12} - 16 r^{3} - 54 \cdot 4 r^{8} r^{4} - 54 r^{8} \cdot - 7 + \frac{18}{r^{3}} (4 r^{4}) + \frac{18}{r^{3}} \cdot - 7 - 144 r$

Step 3.3.6.2.2

Multiply $r^{8}$ by $r^{4}$ by adding the exponents.

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Step 3.3.6.2.2.1

Move $r^{4}$ .

$- 96 r^{12} - 16 r^{3} - 54 \cdot 4 (r^{4} r^{8}) - 54 r^{8} \cdot - 7 + \frac{18}{r^{3}} (4 r^{4}) + \frac{18}{r^{3}} \cdot - 7 - 144 r$

Step 3.3.6.2.2.2

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

$- 96 r^{12} - 16 r^{3} - 54 \cdot 4 r^{4 + 8} - 54 r^{8} \cdot - 7 + \frac{18}{r^{3}} (4 r^{4}) + \frac{18}{r^{3}} \cdot - 7 - 144 r$

Step 3.3.6.2.2.3

Add $4$ and $8$ .

$- 96 r^{12} - 16 r^{3} - 54 \cdot 4 r^{12} - 54 r^{8} \cdot - 7 + \frac{18}{r^{3}} (4 r^{4}) + \frac{18}{r^{3}} \cdot - 7 - 144 r$

Step 3.3.6.2.3

Multiply $- 54$ by $4$ .

$- 96 r^{12} - 16 r^{3} - 216 r^{12} - 54 r^{8} \cdot - 7 + \frac{18}{r^{3}} (4 r^{4}) + \frac{18}{r^{3}} \cdot - 7 - 144 r$

Step 3.3.6.2.4

Multiply $- 7$ by $- 54$ .

$- 96 r^{12} - 16 r^{3} - 216 r^{12} + 378 r^{8} + \frac{18}{r^{3}} (4 r^{4}) + \frac{18}{r^{3}} \cdot - 7 - 144 r$

Step 3.3.6.2.5

Rewrite using the commutative property of multiplication.

$- 96 r^{12} - 16 r^{3} - 216 r^{12} + 378 r^{8} + 4 \frac{18}{r^{3}} r^{4} + \frac{18}{r^{3}} \cdot - 7 - 144 r$

Step 3.3.6.2.6

Multiply $4 \frac{18}{r^{3}}$ .

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Step 3.3.6.2.6.1

Combine $4$ and $\frac{18}{r^{3}}$ .

$- 96 r^{12} - 16 r^{3} - 216 r^{12} + 378 r^{8} + \frac{4 \cdot 18}{r^{3}} r^{4} + \frac{18}{r^{3}} \cdot - 7 - 144 r$

Step 3.3.6.2.6.2

Multiply $4$ by $18$ .

$- 96 r^{12} - 16 r^{3} - 216 r^{12} + 378 r^{8} + \frac{72}{r^{3}} r^{4} + \frac{18}{r^{3}} \cdot - 7 - 144 r$

Step 3.3.6.2.7

Cancel the common factor of $r^{3}$ .

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Step 3.3.6.2.7.1

Factor $r^{3}$ out of $r^{4}$ .

$- 96 r^{12} - 16 r^{3} - 216 r^{12} + 378 r^{8} + \frac{72}{r^{3}} (r^{3} r) + \frac{18}{r^{3}} \cdot - 7 - 144 r$

Step 3.3.6.2.7.2

Cancel the common factor.

$- 96 r^{12} - 16 r^{3} - 216 r^{12} + 378 r^{8} + \frac{72}{r^{3}} (r^{3} r) + \frac{18}{r^{3}} \cdot - 7 - 144 r$

Step 3.3.6.2.7.3

Rewrite the expression.

$- 96 r^{12} - 16 r^{3} - 216 r^{12} + 378 r^{8} + 72 r + \frac{18}{r^{3}} \cdot - 7 - 144 r$

Step 3.3.6.2.8

Multiply $\frac{18}{r^{3}} \cdot - 7$ .

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Step 3.3.6.2.8.1

Combine $\frac{18}{r^{3}}$ and $- 7$ .

$- 96 r^{12} - 16 r^{3} - 216 r^{12} + 378 r^{8} + 72 r + \frac{18 \cdot - 7}{r^{3}} - 144 r$

Step 3.3.6.2.8.2

Multiply $18$ by $- 7$ .

$- 96 r^{12} - 16 r^{3} - 216 r^{12} + 378 r^{8} + 72 r + \frac{- 126}{r^{3}} - 144 r$

Step 3.3.6.2.9

Move the negative in front of the fraction.

$- 96 r^{12} - 16 r^{3} - 216 r^{12} + 378 r^{8} + 72 r - \frac{126}{r^{3}} - 144 r$

Step 3.3.7

Subtract $216 r^{12}$ from $- 96 r^{12}$ .

$- 312 r^{12} - 16 r^{3} + 378 r^{8} + 72 r - \frac{126}{r^{3}} - 144 r$

Step 3.3.8

Subtract $144 r$ from $72 r$ .

$- 312 r^{12} - 16 r^{3} + 378 r^{8} - 72 r - \frac{126}{r^{3}}$

Step 4

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

$f' = - 312 r^{12} - 16 r^{3} + 378 r^{8} - 72 r - \frac{126}{r^{3}}$

Step 5

Replace $f'$ with $\frac{d f}{d r}$ .

$\frac{d f}{d r} = - 312 r^{12} - 16 r^{3} + 378 r^{8} - 72 r - \frac{126}{r^{3}}$