-10d(d+1)=-14

Solution for -10d(d+1)=-14 equation:

-10d(d+1)=-14

We move all terms to the left:

-10d(d+1)-(-14)=0

We add all the numbers together, and all the variables

-10d(d+1)+14=0

We multiply parentheses

-10d^2-10d+14=0

a = -10; b = -10; c = +14;
Δ = b2-4ac
Δ = -102-4·(-10)·14
Δ = 660
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{660}=\sqrt{4*165}=\sqrt{4}*\sqrt{165}=2\sqrt{165}$
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-10)-2\sqrt{165}}{2*-10}=\frac{10-2\sqrt{165}}{-20}
$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-10)+2\sqrt{165}}{2*-10}=\frac{10+2\sqrt{165}}{-20}
$