2x(4x+5)=0

Solution for 2x(4x+5)=0 equation:

2x(4x+5)=0

We multiply parentheses

8x^2+10x=0

a = 8; b = 10; c = 0;
Δ = b2-4ac
Δ = 102-4·8·0
Δ = 100
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{100}=10$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(10)-10}{2*8}=\frac{-20}{16}
=-1+1/4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(10)+10}{2*8}=\frac{0}{16}
=0
$