-y2-4y=-221

Solution for -y2-4y=-221 equation:

-y2-4y=-221

We move all terms to the left:

-y2-4y-(-221)=0

We add all the numbers together, and all the variables

-1y^2-4y+221=0

a = -1; b = -4; c = +221;
Δ = b2-4ac
Δ = -42-4·(-1)·221
Δ = 900
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{900}=30$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-4)-30}{2*-1}=\frac{-26}{-2}
=+13
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-4)+30}{2*-1}=\frac{34}{-2}
=-17
$