Question

f(x)=x-4 and g(x)=x^2. Find (gxf) (-1)

Answer 1

Please help me!

Answer 2

Can you please clarify: what does fxg mean? Do you mean f times g?

Answer 3

yes

Answer 4

f times g

Answer 5

There are actually two ways to do this problem.

Answer 6

May you please show me both.

Answer 7

Since you are given a number for x, that is x = -1 in this problem, you can find the individual function values and multiply them.

Find f(-1):

Find g(-1):

Answer 8

oh! Thank you! After finding both, using x, you multiply them together?

Answer 9

yep. What did you get?

Answer 10

Yes! Thank-You so much!!!!

Answer 11

cool. did you want to see the other way - it involves a bit more algebra...

Answer 12

yes please.

Answer 13

The other way is to multiply the two functions, simplify, then plug in -1 for x:
First:
\[(fg)(x) = (x - 4) * x^2 = x^3 - 4x^2 \]
then
\[ (fg)(-1) = (-1)^3 - 4(-1)^2\]

Should work out to be the same answer.

Answer 14

Okay, I understand both ways! Thank-you!