If we've got two functions $Y=4$ and $y= \sqrt x$ which limits an area with the $Y$-axis. What is the rotation volume of that particular area.
My thoughts about the question is that i put the two equations against each other: $4 = \sqrt x$, $x = 16$.
So my limits are 0 - 16 which we use in the integral,
$2\pi \int x(4- \sqrt x) dx $
But the answer is wrong? How should i think?