7d*d-4d-7=5d

Solution for 7d*d-4d-7=5d equation:

7d*d-4d-7=5d

We move all terms to the left:

7d*d-4d-7-(5d)=0

We add all the numbers together, and all the variables

-9d+7d*d-7=0

Wy multiply elements

7d^2-9d-7=0

a = 7; b = -9; c = -7;
Δ = b2-4ac
Δ = -92-4·7·(-7)
Δ = 277
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-9)-\sqrt{277}}{2*7}=\frac{9-\sqrt{277}}{14}
$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-9)+\sqrt{277}}{2*7}=\frac{9+\sqrt{277}}{14}
$