-3(x-1)(8x+7)=0

Solution for -3(x-1)(8x+7)=0 equation:

-3(x-1)(8x+7)=0

We multiply parentheses ..

-3(+8x^2+7x-8x-7)=0

We multiply parentheses

-24x^2-21x+24x+21=0

We add all the numbers together, and all the variables

-24x^2+3x+21=0

a = -24; b = 3; c = +21;
Δ = b2-4ac
Δ = 32-4·(-24)·21
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{-(3)-45}{2*-24}=\frac{-48}{-48}
=1
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(3)+45}{2*-24}=\frac{42}{-48}
=-7/8
$