12d^2+39d+30=0

Solution for 12d^2+39d+30=0 equation:

12d^2+39d+30=0

a = 12; b = 39; c = +30;
Δ = b2-4ac
Δ = 392-4·12·30
Δ = 81
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{81}=9$
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(39)-9}{2*12}=\frac{-48}{24}
=-2
$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(39)+9}{2*12}=\frac{-30}{24}
=-1+1/4
$