Question

If f(x) = 2x2 - x, find f(-3).

15
21
39

Answer 1

f(-3) is just saying: let x = -3

Answer 2

So,
f(-3) = 2(-3)^2 + 3

Answer 3

f(-3) = 2(9) + 3
f(-3) = 18 + 3
f(-3) = 21

Answer 4

It's like this, when they say 'Find f(-3)', they mean "let x = -3".

Answer 5

So whenever you see 'x' in your equation, you replace it with -3.

Answer 6

So if I had:
f(x) = 2x + 4
And it said:
"Find f(1)"
I would have:
f(1) = 2(1) + 4