(X+15)(5x-7)=0

Solution for (X+15)(5x-7)=0 equation:

(X+15)(5X-7)=0

We multiply parentheses ..

(+5X^2-7X+75X-105)=0

We get rid of parentheses

5X^2-7X+75X-105=0

We add all the numbers together, and all the variables

5X^2+68X-105=0

a = 5; b = 68; c = -105;
Δ = b2-4ac
Δ = 682-4·5·(-105)
Δ = 6724
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{6724}=82$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(68)-82}{2*5}=\frac{-150}{10}
=-15
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(68)+82}{2*5}=\frac{14}{10}
=1+2/5
$