300=(30+2x)*(20+2x)

Solution for 300=(30+2x)*(20+2x) equation:

300=(30+2x)(20+2x)

We move all terms to the left:

300-((30+2x)(20+2x))=0

We add all the numbers together, and all the variables

-((2x+30)(2x+20))+300=0

We multiply parentheses ..

-((+4x^2+40x+60x+600))+300=0


We calculate terms in parentheses: -((+4x^2+40x+60x+600)), so:

(+4x^2+40x+60x+600)

We get rid of parentheses

4x^2+40x+60x+600

We add all the numbers together, and all the variables

4x^2+100x+600

Back to the equation:

-(4x^2+100x+600)


We get rid of parentheses

-4x^2-100x-600+300=0

We add all the numbers together, and all the variables

-4x^2-100x-300=0

a = -4; b = -100; c = -300;
Δ = b2-4ac
Δ = -1002-4·(-4)·(-300)
Δ = 5200
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{5200}=\sqrt{400*13}=\sqrt{400}*\sqrt{13}=20\sqrt{13}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-100)-20\sqrt{13}}{2*-4}=\frac{100-20\sqrt{13}}{-8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-100)+20\sqrt{13}}{2*-4}=\frac{100+20\sqrt{13}}{-8}
$