68.96=4d(d+5)

Solution for 68.96=4d(d+5) equation:

68.96=4d(d+5)

We move all terms to the left:

68.96-(4d(d+5))=0


We calculate terms in parentheses: -(4d(d+5)), so:

4d(d+5)

We multiply parentheses

4d^2+20d

Back to the equation:

-(4d^2+20d)


We get rid of parentheses

-4d^2-20d+68.96=0

a = -4; b = -20; c = +68.96;
Δ = b2-4ac
Δ = -202-4·(-4)·68.96
Δ = 1503.36
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{-(-20)-\sqrt{1503.36}}{2*-4}=\frac{20-\sqrt{1503.36}}{-8}
$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-20)+\sqrt{1503.36}}{2*-4}=\frac{20+\sqrt{1503.36}}{-8}
$