How do you find $[fog](x)$ and $[gof](x)$ given $f(x)=x^2-9$ and $g(x)=x+4$ ?

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Answer 1 · 2016-11-11T21:05:00

The answers are $fog(x)=x^2+8x+7$ and $gof(x)=x^2-5$

$f(x)=x^2-9$

$g(x)=x+4$

$fog(x)=f(g(x))=f(x+4)=(x+4)^2-9=x^2+8x+7$

$gof(x)=g(f(x))=g(x^2-9)=x^2-9+4=x^2-5$

$fog(x)!=gof(x)$

How do you find [fog](x)[fog](x) and [gof](x)[gof](x) given f(x)=x^2-9f(x)=x^2-9 and g(x)=x+4g(x)=x+4?