Question

If f(x) = 5x + 40, what is f(x) when x = -5?
-9
-8
7
15​

Answer 1

15

Explanation:

f(x)=5x+40

f(x)=5(-5)+40

f(x)=-25+40

f(x)=15

Answer 2

15

Explanation:

A function as this f(x) = 5x + 40 means where you have x you need to insert the value of x in the equation. The value of x is -5 hence you write

f(-5) = 5(-5) + 40

Open the bracket by doing 5 x -5 which gives -25

so you have -25 + 40 which you can re-arrange as 40 - 25.

40-25 = 15