(30+2x)*(30+2x)-900=256

Solution for (30+2x)*(30+2x)-900=256 equation:

(30+2x)(30+2x)-900=256

We move all terms to the left:

(30+2x)(30+2x)-900-(256)=0

We add all the numbers together, and all the variables

(2x+30)(2x+30)-900-256=0

We add all the numbers together, and all the variables

(2x+30)(2x+30)-1156=0

We multiply parentheses ..

(+4x^2+60x+60x+900)-1156=0

We get rid of parentheses

4x^2+60x+60x+900-1156=0

We add all the numbers together, and all the variables

4x^2+120x-256=0

a = 4; b = 120; c = -256;
Δ = b2-4ac
Δ = 1202-4·4·(-256)
Δ = 18496
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{18496}=136$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(120)-136}{2*4}=\frac{-256}{8}
=-32
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(120)+136}{2*4}=\frac{16}{8}
=2
$