(42-2x)(28-2x)=480

Solution for (42-2x)(28-2x)=480 equation:

(42-2x)(28-2x)=480

We move all terms to the left:

(42-2x)(28-2x)-(480)=0

We add all the numbers together, and all the variables

(-2x+42)(-2x+28)-480=0

We multiply parentheses ..

(+4x^2-56x-84x+1176)-480=0

We get rid of parentheses

4x^2-56x-84x+1176-480=0

We add all the numbers together, and all the variables

4x^2-140x+696=0

a = 4; b = -140; c = +696;
Δ = b2-4ac
Δ = -1402-4·4·696
Δ = 8464
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{8464}=92$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-140)-92}{2*4}=\frac{48}{8}
=6
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-140)+92}{2*4}=\frac{232}{8}
=29
$