12-28i+15i-35i^2=0

Solution for 12-28i+15i-35i^2=0 equation:

12-28i+15i-35i^2=0

We add all the numbers together, and all the variables

-35i^2-13i+12=0

a = -35; b = -13; c = +12;
Δ = b2-4ac
Δ = -132-4·(-35)·12
Δ = 1849
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$i_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$i_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1849}=43$
$i_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-13)-43}{2*-35}=\frac{-30}{-70}
=3/7
$
$i_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-13)+43}{2*-35}=\frac{56}{-70}
=-4/5
$