(-8-4i)(-3+9i)=0

Solution for (-8-4i)(-3+9i)=0 equation:

(-8-4i)(-3+9i)=0

We add all the numbers together, and all the variables

(-4i-8)(9i-3)=0

We multiply parentheses ..

(-36i^2+12i-72i+24)=0

We get rid of parentheses

-36i^2+12i-72i+24=0

We add all the numbers together, and all the variables

-36i^2-60i+24=0

a = -36; b = -60; c = +24;
Δ = b2-4ac
Δ = -602-4·(-36)·24
Δ = 7056
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$i_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$i_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{7056}=84$
$i_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-60)-84}{2*-36}=\frac{-24}{-72}
=1/3
$
$i_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-60)+84}{2*-36}=\frac{144}{-72}
=-2
$