40d2=39d

Solution for 40d2=39d equation:

40d^2=39d

We move all terms to the left:

40d^2-(39d)=0

a = 40; b = -39; c = 0;
Δ = b2-4ac
Δ = -392-4·40·0
Δ = 1521
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1521}=39$
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-39)-39}{2*40}=\frac{0}{80}
=0
$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-39)+39}{2*40}=\frac{78}{80}
=39/40
$