d=-5d^2+10d+120

Solution for d=-5d^2+10d+120 equation:

d=-5d^2+10d+120

We move all terms to the left:

d-(-5d^2+10d+120)=0

We get rid of parentheses

5d^2-10d+d-120=0

We add all the numbers together, and all the variables

5d^2-9d-120=0

a = 5; b = -9; c = -120;
Δ = b2-4ac
Δ = -92-4·5·(-120)
Δ = 2481
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-9)-\sqrt{2481}}{2*5}=\frac{9-\sqrt{2481}}{10}
$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-9)+\sqrt{2481}}{2*5}=\frac{9+\sqrt{2481}}{10}
$