Question

Given f(x) = 3x^2 +x - 1 and g(x) = 4x+ 5, find (gf)(x).

Answer 1

(gf)(x)=g(f(x))

Answer 2

so would that be

4x+5(3x^2+x-1) ?

Answer 3

\[
g(x) = 4 x + 5\\
g(f(x))= 4 f(x) + 5

\]
Can you finish it?

Answer 4

Oh, wo. okay.

so its 12x^2+4x+1 ?

Answer 5

That is right

Answer 6

hmm, that isn't one of my answer choices..

I think it's supposed to be like this.
4x(3x^2 +x - 1)+ 5 = *12x^3 + 4x^2 -4x + 5*

Answer 7

a. 3x^2 + 5x + 4
b. 12x^3 + 4x^2 - 4x
c. 12x^3 + 19x^2 + x - 5
d. 12x^3 + 19x^2 + 9x - 5


those are the options it gives me.

Answer 8

this is what its asking (3x^2 + x - 1)(4x + 5)

can you solve that?

Answer 9

Oh, well yeah! that's easy


12x^3 +19x^2 + x - 5

Answer 10

You were asked to solve g(x) f(x).

Answer 11

there ya go! :) just name g as the one problem and f as the other, if it says (g + f)(x) then you need to add the two equations. if it says g(f(x)) THEN you would substitute f for x in g's equation

Answer 12

so if i was to solve g(x) f(x)

it would be this: (4x + 5)(3x^2 + x - 1)

@eliassaab

Answer 13

Yes

Answer 14

So that is 12x^3 +19x^2 + x - 5

Answer 15

\[
(4 x+5) \left(3 x^2+x-1\right)=12
x^3+19 x^2+x-5
\]

Answer 16

Yes

Answer 17

ahh you mean (g. f)(x)