-6j(j-9)=0

Solution for -6j(j-9)=0 equation:

-6j(j-9)=0

We multiply parentheses

-6j^2+54j=0

a = -6; b = 54; c = 0;
Δ = b2-4ac
Δ = 542-4·(-6)·0
Δ = 2916
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$j_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$j_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2916}=54$
$j_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(54)-54}{2*-6}=\frac{-108}{-12}
=+9
$
$j_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(54)+54}{2*-6}=\frac{0}{-12}
=0
$