This: $\displaystyle 2\pi\int_1^4 \sqrt{y}\sqrt{1+\frac{1}{4y}}dy$

To get: $\displaystyle \pi\int_1^4\sqrt{4y+1}dy$

I thought they found the common denominator under the radical, distributed the $\displaystyle \sqrt{y}$, then divided by 2. Apparently I'm wrong unless I did the algebra incorrectly.