(2x+5)(2x+5)-25=0

Solution for (2x+5)(2x+5)-25=0 equation:

(2x+5)(2x+5)-25=0

We multiply parentheses ..

(+4x^2+10x+10x+25)-25=0

We get rid of parentheses

4x^2+10x+10x+25-25=0

We add all the numbers together, and all the variables

4x^2+20x=0

a = 4; b = 20; c = 0;
Δ = b2-4ac
Δ = 202-4·4·0
Δ = 400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{400}=20$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(20)-20}{2*4}=\frac{-40}{8}
=-5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(20)+20}{2*4}=\frac{0}{8}
=0
$