9(8-x)(x+5)=0

Solution for 9(8-x)(x+5)=0 equation:

9(8-x)(x+5)=0

We add all the numbers together, and all the variables

9(-1x+8)(x+5)=0

We multiply parentheses ..

9(-1x^2-5x+8x+40)=0

We multiply parentheses

-9x^2-45x+72x+360=0

We add all the numbers together, and all the variables

-9x^2+27x+360=0

a = -9; b = 27; c = +360;
Δ = b2-4ac
Δ = 272-4·(-9)·360
Δ = 13689
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{13689}=117$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(27)-117}{2*-9}=\frac{-144}{-18}
=+8
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(27)+117}{2*-9}=\frac{90}{-18}
=-5
$