-3i(-7+2i)=0

Solution for -3i(-7+2i)=0 equation:

-3i(-7+2i)=0

We add all the numbers together, and all the variables

-3i(2i-7)=0

We multiply parentheses

-6i^2+21i=0

a = -6; b = 21; c = 0;
Δ = b2-4ac
Δ = 212-4·(-6)·0
Δ = 441
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$i_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$i_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{441}=21$
$i_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(21)-21}{2*-6}=\frac{-42}{-12}
=3+1/2
$
$i_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(21)+21}{2*-6}=\frac{0}{-12}
=0
$