d(7d-1)=0

Solution for d(7d-1)=0 equation:

d(7d-1)=0

We multiply parentheses

7d^2-1d=0

a = 7; b = -1; c = 0;
Δ = b2-4ac
Δ = -12-4·7·0
Δ = 1
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1}=1$
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-1)-1}{2*7}=\frac{0}{14}
=0
$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1)+1}{2*7}=\frac{2}{14}
=1/7
$