2700=(x-40)(x+20)

Solution for 2700=(x-40)(x+20) equation:

2700=(x-40)(x+20)

We move all terms to the left:

2700-((x-40)(x+20))=0

We multiply parentheses ..

-((+x^2+20x-40x-800))+2700=0


We calculate terms in parentheses: -((+x^2+20x-40x-800)), so:

(+x^2+20x-40x-800)

We get rid of parentheses

x^2+20x-40x-800

We add all the numbers together, and all the variables

x^2-20x-800

Back to the equation:

-(x^2-20x-800)


We get rid of parentheses

-x^2+20x+800+2700=0

We add all the numbers together, and all the variables

-1x^2+20x+3500=0

a = -1; b = 20; c = +3500;
Δ = b2-4ac
Δ = 202-4·(-1)·3500
Δ = 14400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{14400}=120$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(20)-120}{2*-1}=\frac{-140}{-2}
=+70
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(20)+120}{2*-1}=\frac{100}{-2}
=-50
$