Answer
$\dfrac{76 \pi}{3}$
Work Step by Step
Here, $\dfrac{dx}{dt}= t$ ; $y=2t$
or, $\dfrac{dy}{dt}= 2$
Surface area: $S=\int_0^{\sqrt 5} 2\pi (2t) \sqrt {t^2+4} dt$
Consider $t^2+4=p$
or, $2t=dp$
Thus, $S=\int_4^{9} 2\pi (p)^{1/2} dp$
Hence, $S=2\pi [(\dfrac{2}{3}) p^{(3/2)}]+(4)^{9}=\dfrac{76 \pi}{3}$