(5x+25)(x+5)=90

Solution for (5x+25)(x+5)=90 equation:

(5x+25)(x+5)=90

We move all terms to the left:

(5x+25)(x+5)-(90)=0

We multiply parentheses ..

(+5x^2+25x+25x+125)-90=0

We get rid of parentheses

5x^2+25x+25x+125-90=0

We add all the numbers together, and all the variables

5x^2+50x+35=0

a = 5; b = 50; c = +35;
Δ = b2-4ac
Δ = 502-4·5·35
Δ = 1800
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:

$\sqrt{\Delta}=\sqrt{1800}=\sqrt{900*2}=\sqrt{900}*\sqrt{2}=30\sqrt{2}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(50)-30\sqrt{2}}{2*5}=\frac{-50-30\sqrt{2}}{10}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(50)+30\sqrt{2}}{2*5}=\frac{-50+30\sqrt{2}}{10}
$