Calculus Examples

$g (r) = (8 r^{3} + 7 r + 4) (r^{2} + 3)$

Step 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 $f (r) = 8 r^{3} + 7 r + 4$ and $g (r) = r^{2} + 3$ .

$(8 r^{3} + 7 r + 4) \frac{d}{d r} [r^{2} + 3] + (r^{2} + 3) \frac{d}{d r} [8 r^{3} + 7 r + 4]$

Step 2

Differentiate.

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Step 2.1

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

$(8 r^{3} + 7 r + 4) (\frac{d}{d r} [r^{2}] + \frac{d}{d r} [3]) + (r^{2} + 3) \frac{d}{d r} [8 r^{3} + 7 r + 4]$

Step 2.2

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

$(8 r^{3} + 7 r + 4) (2 r + \frac{d}{d r} [3]) + (r^{2} + 3) \frac{d}{d r} [8 r^{3} + 7 r + 4]$

Step 2.3

Since $3$ is constant with respect to $r$ , the derivative of $3$ with respect to $r$ is $0$ .

$(8 r^{3} + 7 r + 4) (2 r + 0) + (r^{2} + 3) \frac{d}{d r} [8 r^{3} + 7 r + 4]$

Step 2.4

Simplify the expression.

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Step 2.4.1

Add $2 r$ and $0$ .

$(8 r^{3} + 7 r + 4) (2 r) + (r^{2} + 3) \frac{d}{d r} [8 r^{3} + 7 r + 4]$

Step 2.4.2

Move $2$ to the left of $8 r^{3} + 7 r + 4$ .

$2 \cdot (8 r^{3} + 7 r + 4) r + (r^{2} + 3) \frac{d}{d r} [8 r^{3} + 7 r + 4]$

Step 2.5

By the Sum Rule, the derivative of $8 r^{3} + 7 r + 4$ with respect to $r$ is $\frac{d}{d r} [8 r^{3}] + \frac{d}{d r} [7 r] + \frac{d}{d r} [4]$ .

$2 (8 r^{3} + 7 r + 4) r + (r^{2} + 3) (\frac{d}{d r} [8 r^{3}] + \frac{d}{d r} [7 r] + \frac{d}{d r} [4])$

Step 2.6

Since $8$ is constant with respect to $r$ , the derivative of $8 r^{3}$ with respect to $r$ is $8 \frac{d}{d r} [r^{3}]$ .

$2 (8 r^{3} + 7 r + 4) r + (r^{2} + 3) (8 \frac{d}{d r} [r^{3}] + \frac{d}{d r} [7 r] + \frac{d}{d r} [4])$

Step 2.7

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

$2 (8 r^{3} + 7 r + 4) r + (r^{2} + 3) (8 (3 r^{2}) + \frac{d}{d r} [7 r] + \frac{d}{d r} [4])$

Step 2.8

Multiply $3$ by $8$ .

$2 (8 r^{3} + 7 r + 4) r + (r^{2} + 3) (24 r^{2} + \frac{d}{d r} [7 r] + \frac{d}{d r} [4])$

Step 2.9

Since $7$ is constant with respect to $r$ , the derivative of $7 r$ with respect to $r$ is $7 \frac{d}{d r} [r]$ .

$2 (8 r^{3} + 7 r + 4) r + (r^{2} + 3) (24 r^{2} + 7 \frac{d}{d r} [r] + \frac{d}{d r} [4])$

Step 2.10

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

$2 (8 r^{3} + 7 r + 4) r + (r^{2} + 3) (24 r^{2} + 7 \cdot 1 + \frac{d}{d r} [4])$

Step 2.11

Multiply $7$ by $1$ .

$2 (8 r^{3} + 7 r + 4) r + (r^{2} + 3) (24 r^{2} + 7 + \frac{d}{d r} [4])$

Step 2.12

Since $4$ is constant with respect to $r$ , the derivative of $4$ with respect to $r$ is $0$ .

$2 (8 r^{3} + 7 r + 4) r + (r^{2} + 3) (24 r^{2} + 7 + 0)$

Step 2.13

Add $24 r^{2} + 7$ and $0$ .

$2 (8 r^{3} + 7 r + 4) r + (r^{2} + 3) (24 r^{2} + 7)$

Step 3

Simplify.

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Step 3.1