Let f : R → R and g : R → R be functions defined by

Question:

Let $f: R \rightarrow R$ and $g: R \rightarrow R$ be functions defined by $f(x)=5-x^{2}$ and $g(x)=3 x-4$. Then the value of fog $(-1)$ is___________.

Solution:

Given: $f(x)=5-x^{2}$ and $g(x)=3 x-4$

$f o g(-1)=f(g(-1))$

$=f(3(-1)-4)$

$=f(-3-4)$

$=f(-7)$

$=5-(-7)^{2}$

$=5-49$

$=-44$

Hence, the value of fog (–1) is ​–44.

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