0=-2d^2+36d-90

Solution for 0=-2d^2+36d-90 equation:

0=-2d^2+36d-90

We move all terms to the left:

0-(-2d^2+36d-90)=0

We add all the numbers together, and all the variables

-(-2d^2+36d-90)=0

We get rid of parentheses

2d^2-36d+90=0

a = 2; b = -36; c = +90;
Δ = b2-4ac
Δ = -362-4·2·90
Δ = 576
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{576}=24$
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-36)-24}{2*2}=\frac{12}{4}
=3
$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-36)+24}{2*2}=\frac{60}{4}
=15
$