Question

Don't understand how to do these?

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

A. -12
B. 3
C. 6

Answer 1

it just means f(x) = (-3)^2 + x

Answer 2

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

Answer 3

so its just x + 9

Answer 4

No it isn't.

Answer 5

hold up hold up

Answer 6

its 6

Answer 7

my bad

Answer 8

@Jaleena Hey, all you have to do is substitute the number in the parentheses (in this case, -3) for ALL of the x's in the original function. Let's go through another, shall we?

f(x) = x^2 + 8, find f(12)
a) 32
b) 152
c) 76
d) 20

Plug in the value given for x...
f(12) = 12^2 + 8
Remember that 12^2 = 12 x 12, not 12 x 2.
f(x ) = 144 + 8
f(x) = 152
Let me know if you need more practice! These confused the heck out of me at first, too. And the answer for yours is 6.

Answer 9

Thank you! I will let you know for sure. @shopgirl1701