(20+x)(40+x)=1056

Solution for (20+x)(40+x)=1056 equation:

(20+x)(40+x)=1056

We move all terms to the left:

(20+x)(40+x)-(1056)=0

We add all the numbers together, and all the variables

(x+20)(x+40)-1056=0

We multiply parentheses ..

(+x^2+40x+20x+800)-1056=0

We get rid of parentheses

x^2+40x+20x+800-1056=0

We add all the numbers together, and all the variables

x^2+60x-256=0

a = 1; b = 60; c = -256;
Δ = b2-4ac
Δ = 602-4·1·(-256)
Δ = 4624
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4624}=68$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(60)-68}{2*1}=\frac{-128}{2}
=-64
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(60)+68}{2*1}=\frac{8}{2}
=4
$