(7x-15)(5x+25)=0

Solution for (7x-15)(5x+25)=0 equation:

(7x-15)(5x+25)=0

We multiply parentheses ..

(+35x^2+175x-75x-375)=0

We get rid of parentheses

35x^2+175x-75x-375=0

We add all the numbers together, and all the variables

35x^2+100x-375=0

a = 35; b = 100; c = -375;
Δ = b2-4ac
Δ = 1002-4·35·(-375)
Δ = 62500
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{62500}=250$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(100)-250}{2*35}=\frac{-350}{70}
=-5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(100)+250}{2*35}=\frac{150}{70}
=2+1/7
$