Practicing Success
Let $f: R \rightarrow R, g: R \rightarrow R$ and $h: R \rightarrow R$ be differentiable functions such that $f(x)=x^3+3 x+2, g(f(x))=x$ and $h(g(x))=x$ for all $x \in R$. Then, h(g(3)) equals ________. |
38 |
We have, $g(f(x))=x$ and $h(g(g(x)))=x$ for all $x \in R$ $\Rightarrow h(g(g(f(x))))=f(x)$ for all $x \in R$ [Replacing x by f(x)] $\Rightarrow h(g(x))=f(x)$ for all $x \in R$ [∵ g(f(x)) = x] $\Rightarrow h(g(f(x)))=f(f(x))$ for all $x \in R$ [Replacing x by f(x)] $\Rightarrow h(x)=f(f(x))$ for all $x \in R$ [∵ g(f(x)) = x] $h(x)=f(f(x))$ for all $x \in R$. Also, $g(f(x))=x$ for all $x \in R$. Therefore, $f(g(x))=x$ for all $x \in R$. Now, $h(g(3))=f(f(g(3)))=f(3)=27+9+2=38$ |