2n^2-4n=5

Solution for 2n^2-4n=5 equation:

2n^2-4n=5

We move all terms to the left:

2n^2-4n-(5)=0

a = 2; b = -4; c = -5;
Δ = b2-4ac
Δ = -42-4·2·(-5)
Δ = 56
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{56}=\sqrt{4*14}=\sqrt{4}*\sqrt{14}=2\sqrt{14}$
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-4)-2\sqrt{14}}{2*2}=\frac{4-2\sqrt{14}}{4}
$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-4)+2\sqrt{14}}{2*2}=\frac{4+2\sqrt{14}}{4}
$