-4y^2-64y-16=0

Solution for -4y^2-64y-16=0 equation:

-4y^2-64y-16=0

a = -4; b = -64; c = -16;
Δ = b2-4ac
Δ = -642-4·(-4)·(-16)
Δ = 3840
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{3840}=\sqrt{256*15}=\sqrt{256}*\sqrt{15}=16\sqrt{15}$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-64)-16\sqrt{15}}{2*-4}=\frac{64-16\sqrt{15}}{-8}
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-64)+16\sqrt{15}}{2*-4}=\frac{64+16\sqrt{15}}{-8}
$