350=(x+20)(x-5)

Solution for 350=(x+20)(x-5) equation:

350=(x+20)(x-5)

We move all terms to the left:

350-((x+20)(x-5))=0

We multiply parentheses ..

-((+x^2-5x+20x-100))+350=0


We calculate terms in parentheses: -((+x^2-5x+20x-100)), so:

(+x^2-5x+20x-100)

We get rid of parentheses

x^2-5x+20x-100

We add all the numbers together, and all the variables

x^2+15x-100

Back to the equation:

-(x^2+15x-100)


We get rid of parentheses

-x^2-15x+100+350=0

We add all the numbers together, and all the variables

-1x^2-15x+450=0

a = -1; b = -15; c = +450;
Δ = b2-4ac
Δ = -152-4·(-1)·450
Δ = 2025
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2025}=45$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-15)-45}{2*-1}=\frac{-30}{-2}
=+15
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-15)+45}{2*-1}=\frac{60}{-2}
=-30
$