180=(x-25)(x-15)

Solution for 180=(x-25)(x-15) equation:

180=(x-25)(x-15)

We move all terms to the left:

180-((x-25)(x-15))=0

We multiply parentheses ..

-((+x^2-15x-25x+375))+180=0


We calculate terms in parentheses: -((+x^2-15x-25x+375)), so:

(+x^2-15x-25x+375)

We get rid of parentheses

x^2-15x-25x+375

We add all the numbers together, and all the variables

x^2-40x+375

Back to the equation:

-(x^2-40x+375)


We get rid of parentheses

-x^2+40x-375+180=0

We add all the numbers together, and all the variables

-1x^2+40x-195=0

a = -1; b = 40; c = -195;
Δ = b2-4ac
Δ = 402-4·(-1)·(-195)
Δ = 820
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{820}=\sqrt{4*205}=\sqrt{4}*\sqrt{205}=2\sqrt{205}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(40)-2\sqrt{205}}{2*-1}=\frac{-40-2\sqrt{205}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(40)+2\sqrt{205}}{2*-1}=\frac{-40+2\sqrt{205}}{-2}
$