-y^2-15y=36

Solution for -y^2-15y=36 equation:

-y^2-15y=36

We move all terms to the left:

-y^2-15y-(36)=0

We add all the numbers together, and all the variables

-1y^2-15y-36=0

a = -1; b = -15; c = -36;
Δ = b2-4ac
Δ = -152-4·(-1)·(-36)
Δ = 81
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{81}=9$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-15)-9}{2*-1}=\frac{6}{-2}
=-3
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-15)+9}{2*-1}=\frac{24}{-2}
=-12
$