-y2=20y+10

Solution for -y2=20y+10 equation:

-y2=20y+10

We move all terms to the left:

-y2-(20y+10)=0

We add all the numbers together, and all the variables

-1y^2-(20y+10)=0

We get rid of parentheses

-1y^2-20y-10=0

a = -1; b = -20; c = -10;
Δ = b2-4ac
Δ = -202-4·(-1)·(-10)
Δ = 360
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:

$\sqrt{\Delta}=\sqrt{360}=\sqrt{36*10}=\sqrt{36}*\sqrt{10}=6\sqrt{10}$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-20)-6\sqrt{10}}{2*-1}=\frac{20-6\sqrt{10}}{-2}
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-20)+6\sqrt{10}}{2*-1}=\frac{20+6\sqrt{10}}{-2}
$