5x(x+5)=900

Solution for 5x(x+5)=900 equation:

5x(x+5)=900

We move all terms to the left:

5x(x+5)-(900)=0

We multiply parentheses

5x^2+25x-900=0

a = 5; b = 25; c = -900;
Δ = b2-4ac
Δ = 252-4·5·(-900)
Δ = 18625
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:

$\sqrt{\Delta}=\sqrt{18625}=\sqrt{25*745}=\sqrt{25}*\sqrt{745}=5\sqrt{745}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(25)-5\sqrt{745}}{2*5}=\frac{-25-5\sqrt{745}}{10}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(25)+5\sqrt{745}}{2*5}=\frac{-25+5\sqrt{745}}{10}
$