d^2=14d+49=0

Solution for d^2=14d+49=0 equation:

d^2=14d+49=0

We move all terms to the left:

d^2-(14d+49)=0

We get rid of parentheses

d^2-14d-49=0

a = 1; b = -14; c = -49;
Δ = b2-4ac
Δ = -142-4·1·(-49)
Δ = 392
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:

$\sqrt{\Delta}=\sqrt{392}=\sqrt{196*2}=\sqrt{196}*\sqrt{2}=14\sqrt{2}$
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-14)-14\sqrt{2}}{2*1}=\frac{14-14\sqrt{2}}{2}
$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-14)+14\sqrt{2}}{2*1}=\frac{14+14\sqrt{2}}{2}
$