(viii) f(x2+3)=2(x2+3)+3=2x2+6+3=2x2+9\begin{aligned} f(x^2+3)&=\sqrt{2(x^2+3)+3}\\ &=\sqrt{2x^2+6+3}\\ &=\sqrt{2x^2+9} \end{aligned}f(x2+3)=2(x2+3)+3=2x2+6+3=2x2+9 f(x2+3)=2x2+9\boxed{f(x^2+3)=\sqrt{2x^2+9}}f(x2+3)=2x2+9