Answer = $- \frac{1}{2}$
It's an $∞ - ∞$ indeterminate form. Hence, We first convert it into $ \frac{0}{0}$ form and then apply D'Hopital's rule.
To convert it into $ \frac{0}{0}$ form... Take $y^2$ out of the Square root expression and then $y$ out from the whole expression.