-9x(x+5)=0

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

-9x(x+5)=0

We multiply parentheses

-9x^2-45x=0

a = -9; b = -45; c = 0;
Δ = b2-4ac
Δ = -452-4·(-9)·0
Δ = 2025
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2025}=45$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-45)-45}{2*-9}=\frac{0}{-18}
=0
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-45)+45}{2*-9}=\frac{90}{-18}
=-5
$