9c^2-39c=30

Solution for 9c^2-39c=30 equation:

9c^2-39c=30

We move all terms to the left:

9c^2-39c-(30)=0

a = 9; b = -39; c = -30;
Δ = b2-4ac
Δ = -392-4·9·(-30)
Δ = 2601
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2601}=51$
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-39)-51}{2*9}=\frac{-12}{18}
=-2/3
$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-39)+51}{2*9}=\frac{90}{18}
=5
$