25(x-7)(x-9)=0

Solution for 25(x-7)(x-9)=0 equation:

25(x-7)(x-9)=0

We multiply parentheses ..

25(+x^2-9x-7x+63)=0

We multiply parentheses

25x^2-225x-175x+1575=0

We add all the numbers together, and all the variables

25x^2-400x+1575=0

a = 25; b = -400; c = +1575;
Δ = b2-4ac
Δ = -4002-4·25·1575
Δ = 2500
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2500}=50$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-400)-50}{2*25}=\frac{350}{50}
=7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-400)+50}{2*25}=\frac{450}{50}
=9
$