Question

Given ƒ(x) = 9x + 54, find x when ƒ(x) = 18. A) −6 B) −4 C) 3 D) 8

Answer 1

Answer: B

Explanation:

Well, they told you what f(x) equals. So make the function of f(x) equal to the value they gave, 18

`18=9x+54`

Subtract 54 from both sides to get:

`-36=9x`

Divide both sides by 9 to get x = -4

Answer 2

-4 =x

Explanation:

ƒ(x) = 9x + 54

Let f(x) = 18

18 = 9x+54

Subtract 54 from each side

18-54 = 9x + 54-54

-36 = 9x

Divide each side by 9

-36/9 = 9x/9

-4 =x