180=(x-4)(x+9)

Solution for 180=(x-4)(x+9) equation:

180=(x-4)(x+9)

We move all terms to the left:

180-((x-4)(x+9))=0

We multiply parentheses ..

-((+x^2+9x-4x-36))+180=0


We calculate terms in parentheses: -((+x^2+9x-4x-36)), so:

(+x^2+9x-4x-36)

We get rid of parentheses

x^2+9x-4x-36

We add all the numbers together, and all the variables

x^2+5x-36

Back to the equation:

-(x^2+5x-36)


We get rid of parentheses

-x^2-5x+36+180=0

We add all the numbers together, and all the variables

-1x^2-5x+216=0

a = -1; b = -5; c = +216;
Δ = b2-4ac
Δ = -52-4·(-1)·216
Δ = 889
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-5)-\sqrt{889}}{2*-1}=\frac{5-\sqrt{889}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-5)+\sqrt{889}}{2*-1}=\frac{5+\sqrt{889}}{-2}
$