(40-2x)(60-2x)=0

Solution for (40-2x)(60-2x)=0 equation:

(40-2x)(60-2x)=0

We add all the numbers together, and all the variables

(-2x+40)(-2x+60)=0

We multiply parentheses ..

(+4x^2-120x-80x+2400)=0

We get rid of parentheses

4x^2-120x-80x+2400=0

We add all the numbers together, and all the variables

4x^2-200x+2400=0

a = 4; b = -200; c = +2400;
Δ = b2-4ac
Δ = -2002-4·4·2400
Δ = 1600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1600}=40$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-200)-40}{2*4}=\frac{160}{8}
=20
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-200)+40}{2*4}=\frac{240}{8}
=30
$