college algebra
2006-11-24 04:22:09 · 5 answers · asked by koka 1 in Science & Mathematics ➔ Mathematics
f(x)=-5(x)+7
f0g=-5[-9x^2-4x+5]+7
=45x^2+20x-25+7
=45x^2+20x-18
fog(-9)
=45(-9)^2+20(-9)-18
=3645-180-18
=3447
2006-11-24 04:27:05 · answer #1 · answered by raj 7 · 0⤊ 1⤋
f o g means f(g(x))
f(x) = -5x + 7
g(x) = -9x^2 - 4x + 5
Here's how these work: Take your 'f(x)'....if you wanted to know what f(1) was.....that's just: f(1) = -5*(1) + 7
Right?
Then you'd do the arithmetic and come up with: f(1) = 2
Same thing goes with these 'composition' of functions.
f(g(x)) = -5[-9x^2 - 4x + 5] + 7
==> 45x^2 + 20x - 25 + 7
==> 45x^2 + 20x -18
So...f o g = 45x^2 + 20x -18
Do you see?
Now.....you SHOULD be able to do f o g(-9) yourself....it's the SAME kind of thing as I did above with f(1).
2006-11-24 12:29:20 · answer #2 · answered by Anonymous · 0⤊ 0⤋
f o g = -5(-9x^2-4x+5) + 7 = 45x^2 + 20x -18
2006-11-24 12:46:59 · answer #3 · answered by ag_iitkgp 7 · 0⤊ 0⤋
the answer is 3447 b/c :
g(-9) = -9(-9)^2 - 4(-9) +5
= -688
f(g) = -5(-688)+7
= 3447
2006-11-24 12:37:53 · answer #4 · answered by Gardenia 6 · 0⤊ 0⤋
plug in -9 for all the x's in the equation and then multiply the answers together
2006-11-24 12:25:22 · answer #5 · answered by jrtootsiepop 3 · 0⤊ 1⤋