-5(x-5)(x+9)=0

Solution for -5(x-5)(x+9)=0 equation:

-5(x-5)(x+9)=0

We multiply parentheses ..

-5(+x^2+9x-5x-45)=0

We multiply parentheses

-5x^2-45x+25x+225=0

We add all the numbers together, and all the variables

-5x^2-20x+225=0

a = -5; b = -20; c = +225;
Δ = b2-4ac
Δ = -202-4·(-5)·225
Δ = 4900
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4900}=70$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-20)-70}{2*-5}=\frac{-50}{-10}
=+5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-20)+70}{2*-5}=\frac{90}{-10}
=-9
$