9(c+4)(c-5)=0

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

9(c+4)(c-5)=0

We multiply parentheses ..

9(+c^2-5c+4c-20)=0

We multiply parentheses

9c^2-45c+36c-180=0

We add all the numbers together, and all the variables

9c^2-9c-180=0

a = 9; b = -9; c = -180;
Δ = b2-4ac
Δ = -92-4·9·(-180)
Δ = 6561
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{6561}=81$
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-9)-81}{2*9}=\frac{-72}{18}
=-4
$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-9)+81}{2*9}=\frac{90}{18}
=5
$