-4(y-5)(-y-9)=0

Solution for -4(y-5)(-y-9)=0 equation:

-4(y-5)(-y-9)=0

We add all the numbers together, and all the variables

-4(y-5)(-1y-9)=0

We multiply parentheses ..

-4(-1y^2-9y+5y+45)=0

We multiply parentheses

4y^2+36y-20y-180=0

We add all the numbers together, and all the variables

4y^2+16y-180=0

a = 4; b = 16; c = -180;
Δ = b2-4ac
Δ = 162-4·4·(-180)
Δ = 3136
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{3136}=56$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(16)-56}{2*4}=\frac{-72}{8}
=-9
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(16)+56}{2*4}=\frac{40}{8}
=5
$