9i(-2i+9)=0

Solution for 9i(-2i+9)=0 equation:

9i(-2i+9)=0

We multiply parentheses

-18i^2+81i=0

a = -18; b = 81; c = 0;
Δ = b2-4ac
Δ = 812-4·(-18)·0
Δ = 6561
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$i_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$i_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{6561}=81$
$i_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(81)-81}{2*-18}=\frac{-162}{-36}
=4+1/2
$
$i_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(81)+81}{2*-18}=\frac{0}{-36}
=0
$