(20+2x)(30+2x)=336

Solution for (20+2x)(30+2x)=336 equation:

(20+2x)(30+2x)=336

We move all terms to the left:

(20+2x)(30+2x)-(336)=0

We add all the numbers together, and all the variables

(2x+20)(2x+30)-336=0

We multiply parentheses ..

(+4x^2+60x+40x+600)-336=0

We get rid of parentheses

4x^2+60x+40x+600-336=0

We add all the numbers together, and all the variables

4x^2+100x+264=0

a = 4; b = 100; c = +264;
Δ = b2-4ac
Δ = 1002-4·4·264
Δ = 5776
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{5776}=76$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(100)-76}{2*4}=\frac{-176}{8}
=-22
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(100)+76}{2*4}=\frac{-24}{8}
=-3
$