(30+x)(30+x)=1800

Solution for (30+x)(30+x)=1800 equation:

(30+x)(30+x)=1800

We move all terms to the left:

(30+x)(30+x)-(1800)=0

We add all the numbers together, and all the variables

(x+30)(x+30)-1800=0

We multiply parentheses ..

(+x^2+30x+30x+900)-1800=0

We get rid of parentheses

x^2+30x+30x+900-1800=0

We add all the numbers together, and all the variables

x^2+60x-900=0

a = 1; b = 60; c = -900;
Δ = b2-4ac
Δ = 602-4·1·(-900)
Δ = 7200
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:

$\sqrt{\Delta}=\sqrt{7200}=\sqrt{3600*2}=\sqrt{3600}*\sqrt{2}=60\sqrt{2}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(60)-60\sqrt{2}}{2*1}=\frac{-60-60\sqrt{2}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(60)+60\sqrt{2}}{2*1}=\frac{-60+60\sqrt{2}}{2}
$