(80-2x)(60-2x)=2400

Solution for (80-2x)(60-2x)=2400 equation:

(80-2x)(60-2x)=2400

We move all terms to the left:

(80-2x)(60-2x)-(2400)=0

We add all the numbers together, and all the variables

(-2x+80)(-2x+60)-2400=0

We multiply parentheses ..

(+4x^2-120x-160x+4800)-2400=0

We get rid of parentheses

4x^2-120x-160x+4800-2400=0

We add all the numbers together, and all the variables

4x^2-280x+2400=0

a = 4; b = -280; c = +2400;
Δ = b2-4ac
Δ = -2802-4·4·2400
Δ = 40000
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{40000}=200$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-280)-200}{2*4}=\frac{80}{8}
=10
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-280)+200}{2*4}=\frac{480}{8}
=60
$