Friday, February 25, 2011

Given f(x)=2x+1 and g(x)=x+2 solve the equation gogog(x)=fofof(x)

We'll determine (gogog)(x) =
g(g(g(x)))


g(g(g(x))) = g(g(x)) +
2


g(g(g(x))) = [g(x) + 2] +
2


g(g(g(x))) = (x + 2 + 2) +
2


g(g(g(x))) = x + 6


We'll
determine (fofof)(x) = f(f(f(x)))


f(f(f(x))) = 2f(f(x)) +
1


f(f(f(x))) = 2[2f(x) + 1] +
1


f(f(f(x))) = 4f(x) + 2 +
1


f(f(f(x))) = 4(2x + 1) +
3


f(f(f(x))) = 8x + 4 +
3


f(f(f(x))) = 8x + 7


We'll
solve the equation:


x + 6 = 8x +
7


We'll subtract 8x + 7 both
sides:


x - 8x + 6 - 7 = 0


-7x
- 1 = 0


We'll add 1:


-7x =
1


We'll divide by -7 both
sides:


x =
-1/7


The solution of the equation g(g(g(x)))
= f(f(f(x))) is x = -1/7.

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