SOLUTION: help f(x) = 3x - 5 g(x) = 6x2 + 2x Find: g(f(x)) f(x) = 2x + 3 g(x) = 5x2 + 6x - 5 Find: f(g(x)) i can not figure these 2 out thanks for your help

Algebra ->  Rational-functions -> SOLUTION: help f(x) = 3x - 5 g(x) = 6x2 + 2x Find: g(f(x)) f(x) = 2x + 3 g(x) = 5x2 + 6x - 5 Find: f(g(x)) i can not figure these 2 out thanks for your help      Log On


   

Question 547348: help
f(x) = 3x - 5
g(x) = 6x2 + 2x
Find: g(f(x))


f(x) = 2x + 3
g(x) = 5x2 + 6x - 5
Find: f(g(x))

i can not figure these 2 out
thanks for your help
Answer by lwsshak3(11628) About Me  (Show Source):
You can put this solution on YOUR website!
f(x) = 3x - 5
g(x) = 6x^2 + 2x
Find: g(f(x))
method: for each x in g, substitute (3x-5)
g[f(x)]=6(3x-5)^2+2(3x-5)
=6(9x^2-30x+25)+6x-10
=54x^2-180x+150+6x-10
g[f(x)]=54x^2-174x+140

f(x) = 2x + 3
g(x) = 5x^2 + 6x - 5
Find: f(g(x))
for each x in f, substitute (5x^2+6x-5)
f[g(x)]=2(5x^2+6x-5)+3
=10x^2+12x-10+3
f[g(x)]=10x^2+12x-7