5i(-2-4i)=0

Solution for 5i(-2-4i)=0 equation:

5i(-2-4i)=0

We add all the numbers together, and all the variables

5i(-4i-2)=0

We multiply parentheses

-20i^2-10i=0

a = -20; b = -10; c = 0;
Δ = b2-4ac
Δ = -102-4·(-20)·0
Δ = 100
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$i_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$i_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{100}=10$
$i_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-10)-10}{2*-20}=\frac{0}{-40}
=0
$
$i_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-10)+10}{2*-20}=\frac{20}{-40}
=-1/2
$