(15-8x)(7x+3)=0

Solution for (15-8x)(7x+3)=0 equation:

(15-8x)(7x+3)=0

We add all the numbers together, and all the variables

(-8x+15)(7x+3)=0

We multiply parentheses ..

(-56x^2-24x+105x+45)=0

We get rid of parentheses

-56x^2-24x+105x+45=0

We add all the numbers together, and all the variables

-56x^2+81x+45=0

a = -56; b = 81; c = +45;
Δ = b2-4ac
Δ = 812-4·(-56)·45
Δ = 16641
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{16641}=129$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(81)-129}{2*-56}=\frac{-210}{-112}
=1+7/8
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(81)+129}{2*-56}=\frac{48}{-112}
=-3/7
$