5x(5x+8)=0

Solution for 5x(5x+8)=0 equation:

5x(5x+8)=0

We multiply parentheses

25x^2+40x=0

a = 25; b = 40; c = 0;
Δ = b2-4ac
Δ = 402-4·25·0
Δ = 1600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1600}=40$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(40)-40}{2*25}=\frac{-80}{50}
=-1+3/5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(40)+40}{2*25}=\frac{0}{50}
=0
$