-9(8x+7)(x+1)=0

Solution for -9(8x+7)(x+1)=0 equation:

-9(8x+7)(x+1)=0

We multiply parentheses ..

-9(+8x^2+8x+7x+7)=0

We multiply parentheses

-72x^2-72x-63x-63=0

We add all the numbers together, and all the variables

-72x^2-135x-63=0

a = -72; b = -135; c = -63;
Δ = b2-4ac
Δ = -1352-4·(-72)·(-63)
Δ = 81
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{81}=9$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-135)-9}{2*-72}=\frac{126}{-144}
=-7/8
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-135)+9}{2*-72}=\frac{144}{-144}
=-1
$