#### Need solution for RD Sharma Class 12 Chapter Functions Exercise 2.3 Question 4 Sub question (iii) maths textbook solution.

Answer : $f \circ f(x)=4 x+15$

Given : Here given that $f(x)=2 x+5 \text { and } g(x)=x^{2}+1$

Here we have to compute $f\; o\; f$

Solution :

Since $f(x)$ and $g(x)$ are polynomials

$\Rightarrow \quad f: R \rightarrow R \text { and } g: R \rightarrow R$

\begin{aligned} \Rightarrow \quad f \circ f(x) &=f(f(x)) \\ &=f(2 x+5) \\ &=2(2 x+5)+5 \\ &=4 x+10+5 \\ &=4 x+15 \end{aligned}

Hence, $f \circ f(x)=4 x+15$