0=15d^2+16d-15

Solution for 0=15d^2+16d-15 equation:

0=15d^2+16d-15

We move all terms to the left:

0-(15d^2+16d-15)=0

We add all the numbers together, and all the variables

-(15d^2+16d-15)=0

We get rid of parentheses

-15d^2-16d+15=0

a = -15; b = -16; c = +15;
Δ = b2-4ac
Δ = -162-4·(-15)·15
Δ = 1156
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1156}=34$
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-16)-34}{2*-15}=\frac{-18}{-30}
=3/5
$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-16)+34}{2*-15}=\frac{50}{-30}
=-1+2/3
$