-20y^2+56y+306=0

Solution for -20y^2+56y+306=0 equation:

-20y^2+56y+306=0

a = -20; b = 56; c = +306;
Δ = b2-4ac
Δ = 562-4·(-20)·306
Δ = 27616
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:

$\sqrt{\Delta}=\sqrt{27616}=\sqrt{16*1726}=\sqrt{16}*\sqrt{1726}=4\sqrt{1726}$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(56)-4\sqrt{1726}}{2*-20}=\frac{-56-4\sqrt{1726}}{-40}
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(56)+4\sqrt{1726}}{2*-20}=\frac{-56+4\sqrt{1726}}{-40}
$