Question

Given the function f(x) = 5x - 3(3x + 7), determine the value of x when f(x) = -18.

Answer 1

x = -
`(3)/(4)`

Explanation:

given

f(x) = 5x - 3(3x + 7) and f(x) = - 18

equate right sides of both , that is

5x - 3(3x + 7) = - 18 ← distribute parenthesis on left side and simplify

5x - 9x - 21 = - 18

- 4x - 21 = - 18 ( add 21 to both sides )

- 4x - 21 + 21 = - 18 + 21 ( simplify )

- 4x = 3 ( divide both sides by - 4 )

`(-4)/(-4)` x =
`(3)/(-4)` , then

x = -
`(3)/(4)`