Precalculus Examples

f (x) = 3 x + 5

$f (x) = 3 x + 5$ ,

g (x) = x^{3}

$g (x) = x^{3}$ ,

(g \circ f)

$(g \circ f)$

Step 1

Set up the composite result function.

g (f (x))

$g (f (x))$

Step 2

Evaluate

g (3 x + 5)

$g (3 x + 5)$ by substituting in the value of

f

$f$ into

g

$g$ .

g (3 x + 5) = {(3 x + 5)}^{3}

$g (3 x + 5) = {(3 x + 5)}^{3}$

Step 3

Use the Binomial Theorem.

g (3 x + 5) = {(3 x)}^{3} + 3 {(3 x)}^{2} \cdot 5 + 3 (3 x) \cdot 5^{2} + 5^{3}

$g (3 x + 5) = {(3 x)}^{3} + 3 {(3 x)}^{2} \cdot 5 + 3 (3 x) \cdot 5^{2} + 5^{3}$

Step 4

Simplify each term.

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Step 4.1

Apply the product rule to

3 x

$3 x$ .

g (3 x + 5) = 3^{3} x^{3} + 3 {(3 x)}^{2} \cdot 5 + 3 (3 x) \cdot 5^{2} + 5^{3}

$g (3 x + 5) = 3^{3} x^{3} + 3 {(3 x)}^{2} \cdot 5 + 3 (3 x) \cdot 5^{2} + 5^{3}$

Step 4.2

Raise

3

$3$ to the power of

3

$3$ .

g (3 x + 5) = 27 x^{3} + 3 {(3 x)}^{2} \cdot 5 + 3 (3 x) \cdot 5^{2} + 5^{3}

$g (3 x + 5) = 27 x^{3} + 3 {(3 x)}^{2} \cdot 5 + 3 (3 x) \cdot 5^{2} + 5^{3}$

Step 4.3

Apply the product rule to

3 x

$3 x$ .

g (3 x + 5) = 27 x^{3} + 3 (3^{2} x^{2}) \cdot 5 + 3 (3 x) \cdot 5^{2} + 5^{3}

$g (3 x + 5) = 27 x^{3} + 3 (3^{2} x^{2}) \cdot 5 + 3 (3 x) \cdot 5^{2} + 5^{3}$

Step 4.4

Multiply

3

$3$ by

3^{2}

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

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Step 4.4.1

Move

3^{2}

$3^{2}$ .

g (3 x + 5) = 27 x^{3} + 3^{2} \cdot (3 x^{2}) \cdot 5 + 3 (3 x) \cdot 5^{2} + 5^{3}

$g (3 x + 5) = 27 x^{3} + 3^{2} \cdot (3 x^{2}) \cdot 5 + 3 (3 x) \cdot 5^{2} + 5^{3}$

Step 4.4.2

Multiply

3^{2}

$3^{2}$ by

3

$3$ .

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Step 4.4.2.1

Raise

3

$3$ to the power of

1

$1$ .

g (3 x + 5) = 27 x^{3} + 3^{2} \cdot (3 x^{2}) \cdot 5 + 3 (3 x) \cdot 5^{2} + 5^{3}

$g (3 x + 5) = 27 x^{3} + 3^{2} \cdot (3 x^{2}) \cdot 5 + 3 (3 x) \cdot 5^{2} + 5^{3}$

Step 4.4.2.2

Use the power rule

a^{m} a^{n} = a^{m + n}

$a^{m} a^{n} = a^{m + n}$ to combine exponents.

g (3 x + 5) = 27 x^{3} + 3^{2 + 1} x^{2} \cdot 5 + 3 (3 x) \cdot 5^{2} + 5^{3}

$g (3 x + 5) = 27 x^{3} + 3^{2 + 1} x^{2} \cdot 5 + 3 (3 x) \cdot 5^{2} + 5^{3}$

g (3 x + 5) = 27 x^{3} + 3^{2 + 1} x^{2} \cdot 5 + 3 (3 x) \cdot 5^{2} + 5^{3}

$g (3 x + 5) = 27 x^{3} + 3^{2 + 1} x^{2} \cdot 5 + 3 (3 x) \cdot 5^{2} + 5^{3}$

Step 4.4.3

Add

2

$2$ and

1

$1$ .

g (3 x + 5) = 27 x^{3} + 3^{3} x^{2} \cdot 5 + 3 (3 x) \cdot 5^{2} + 5^{3}

$g (3 x + 5) = 27 x^{3} + 3^{3} x^{2} \cdot 5 + 3 (3 x) \cdot 5^{2} + 5^{3}$

g (3 x + 5) = 27 x^{3} + 3^{3} x^{2} \cdot 5 + 3 (3 x) \cdot 5^{2} + 5^{3}

$g (3 x + 5) = 27 x^{3} + 3^{3} x^{2} \cdot 5 + 3 (3 x) \cdot 5^{2} + 5^{3}$

Step 4.5

Raise

3

$3$ to the power of

3

$3$ .

g (3 x + 5) = 27 x^{3} + 27 x^{2} \cdot 5 + 3 (3 x) \cdot 5^{2} + 5^{3}

$g (3 x + 5) = 27 x^{3} + 27 x^{2} \cdot 5 + 3 (3 x) \cdot 5^{2} + 5^{3}$

Step 4.6

Multiply

5

$5$ by

27

$27$ .

g (3 x + 5) = 27 x^{3} + 135 x^{2} + 3 (3 x) \cdot 5^{2} + 5^{3}

$g (3 x + 5) = 27 x^{3} + 135 x^{2} + 3 (3 x) \cdot 5^{2} + 5^{3}$

Step 4.7

Multiply

3

$3$ by

3

$3$ .

g (3 x + 5) = 27 x^{3} + 135 x^{2} + 9 x \cdot 5^{2} + 5^{3}

$g (3 x + 5) = 27 x^{3} + 135 x^{2} + 9 x \cdot 5^{2} + 5^{3}$

Step 4.8

Raise

5

$5$ to the power of

2

$2$ .

g (3 x + 5) = 27 x^{3} + 135 x^{2} + 9 x \cdot 25 + 5^{3}

$g (3 x + 5) = 27 x^{3} + 135 x^{2} + 9 x \cdot 25 + 5^{3}$

Step 4.9

Multiply

25

$25$ by

9

$9$ .

g (3 x + 5) = 27 x^{3} + 135 x^{2} + 225 x + 5^{3}

$g (3 x + 5) = 27 x^{3} + 135 x^{2} + 225 x + 5^{3}$

Step 4.10

Raise

5

$5$ to the power of

3

$3$ .

g (3 x + 5) = 27 x^{3} + 135 x^{2} + 225 x + 125

$g (3 x + 5) = 27 x^{3} + 135 x^{2} + 225 x + 125$

g (3 x + 5) = 27 x^{3} + 135 x^{2} + 225 x + 125

$g (3 x + 5) = 27 x^{3} + 135 x^{2} + 225 x + 125$

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