30d^2-20d-10=0

Solution for 30d^2-20d-10=0 equation:

30d^2-20d-10=0

a = 30; b = -20; c = -10;
Δ = b2-4ac
Δ = -202-4·30·(-10)
Δ = 1600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1600}=40$
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-20)-40}{2*30}=\frac{-20}{60}
=-1/3
$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-20)+40}{2*30}=\frac{60}{60}
=1
$