how to do this qr problem?

[issa]

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Shot at 2007-08-10

 

[red88m]

Plug n chug:
f(g(x)) = 3(-2x+5)+2
g(f(x)) = -2(-6x+1)+5
f(x)g(x)= (3x+2)(-2x+5)

I didn't work these all the way out...I'm 99.9% they're right.

 

[rimmies]

f(g(x)) just take the f(x) formula and replace the x with the g(x) forumla. do the opposite for the other one. so, f(g(x)) = 3(-2x+5)+2=-6x+17

the last one you just foil the two formulas.

 

[rimmies]

yeah, so I worked them out, and had to find a pen....

 

[DividedByZero]

Plug n chug:
f(g(x)) = 3(-2x+5)+2
g(f(x)) = -2(-6x+1)+5
f(x)g(x)= (3x+2)(-2x+5)

I didn't work these all the way out...I'm 99.9% they're right.

wouldn't g(f(x)) be -2(3x+2)+5? which would then equal -6x+1?

 

[SupderDuper]

Shot at 2007-08-10

f(x) = 3x + 2
g(x) = -2x + 5

So, f(g(x)) = 3 * ( -2x + 5 ) +2 = -6x + 15 + 2 = -6x + 17
Also, g(f(x)) = -2 * ( 3x + 2 ) + 5 = -6x - 4 + 5 = -6x + 1

f(x) * g(x) = (3x + 2) * (-2x + 5) = -6x^2 + 15x - 4x + 10
= -6x^2 + 11x + 10

 

[red88m]

wouldn't g(f(x)) be -2(3x+2)+5? which would then equal -6x+1?

Ha yeah. That was the .1% I was talking about. The in-a-hurry margin of error.