Given,
f(x)={\begin{matrix}\frac{1}{x},x\geq 2 \\ a{x}^{2}+2b,-2<x<2 \\ -\frac{1}{x},x\leq -2\end{matrix}
Also given f(x) is differentiable on R
So, finding LHD and RHD at x=2 we get,
−x21=2ax
⇒4−1=4a
⇒a=16−1
Now, for function to be continuous at x=2 we get,
21=4a+2b
⇒21=16−4+2b
⇒b=83
Hence, 48(a+b)=48(83−161)
⇒48(a+b)=48(165)=15