Posted by Jess on Tuesday, April 28, 2009 at 7:11am.
no, one term was right, but your constant is wrong.
do it this way :
f(x) = -3x + 9
g(x) = 8x + 7
then g(f(x))
= g(-3x+9)
= 8(-3x+9) + 7
= -24x + 72 + 7
= -24x + 79
and f(g(x))
= f(8x+7)
= -3(8x+7) + 9
= -24x - 21 + 9
= -24x - 12
Thank you so much! I've been sitting here for hours. Only 4 to go. Thanks :)
2 down.
I'm having trouble here
f(x) = 4x + 2
h(x) = -7x - 5
Find f(h(x))
I tried doing it how it was done above, but i'm not getting an answer listed.
= f(-7x - 5)
= 4x(-7x-5)+ 2
= 28x^2-20+2
= 28x^2-18
Where am I going wrong :| ?
ALSO -
f(x) = 4x-3
g(x) = x2-2
Find f(3a-4)
from
= f(-7x - 5) to
= 4x(-7x-5)+ 2
you are replacing the x, so don't leave the x there.
should be
= 4(-7x-5)+ 2
= -28x - 20 + 2
= -28x - 18
for
f(x) = 4x-3
g(x) = x2-2
Find f(3a-4)
I will assume g(x) = x^2 - 2
then f(3a-4)
= 4(3a-4) - 3
= 12a - 16 - 3
= 12a - 19
the x in f(x) was merely replaced by 3a-4, so you have to replace it everywhere that you see an x.
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