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

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

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

We move all terms to the left:

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

We add all the numbers together, and all the variables

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

We multiply parentheses ..

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

We get rid of parentheses

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

We add all the numbers together, and all the variables

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