Calculus 8th Edition

$L = \int^{4}_{1}\sqrt{1+(\frac{1}{2\sqrt{y}}-1)^{2}}dy$
$x = \sqrt{y} - y$ then $dx/dy = 1/(2\sqrt{y}) -1$ and $1+(dx/dy)^{2} = 1+(\frac{1}{2\sqrt{y}}-1)^{2}$ $L = \int^{4}_{1}\sqrt{1+(\frac{1}{2\sqrt{y}}-1)^{2}}dy$