25x^2-25x-25x+25=400

Solution for 25x^2-25x-25x+25=400 equation:

25x^2-25x-25x+25=400

We move all terms to the left:

25x^2-25x-25x+25-(400)=0

We add all the numbers together, and all the variables

25x^2-50x-375=0

a = 25; b = -50; c = -375;
Δ = b2-4ac
Δ = -502-4·25·(-375)
Δ = 40000
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{40000}=200$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-50)-200}{2*25}=\frac{-150}{50}
=-3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-50)+200}{2*25}=\frac{250}{50}
=5
$