Precalculus Examples

let $f (x) = 5 x^{2} + 15 x - 16$ and find $f (- 4)$

Step 1

Replace the variable $x$ with $- 4$ in the expression.

$f (- 4) = 5 {(- 4)}^{2} + 15 (- 4) - 16$

Step 2

Simplify $5 {(- 4)}^{2} + 15 (- 4) - 16$ .

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Step 2.1

Remove parentheses.

$5 {(- 4)}^{2} + 15 (- 4) - 16$

Step 2.2

Simplify each term.

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Step 2.2.1

Raise $- 4$ to the power of $2$ .

$5 \cdot 16 + 15 (- 4) - 16$

Step 2.2.2

Multiply $5$ by $16$ .

$80 + 15 (- 4) - 16$

Step 2.2.3

Multiply $15$ by $- 4$ .

$80 - 60 - 16$

Step 2.3

Simplify by subtracting numbers.

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Step 2.3.1

Subtract $60$ from $80$ .

$20 - 16$

Step 2.3.2

Subtract $16$ from $20$ .

$4$