n2+2n=15,8

Solution for n2+2n=15,8 equation:

n2+2n=15.8

We move all terms to the left:

n2+2n-(15.8)=0

We add all the numbers together, and all the variables

n^2+2n-15.8=0

a = 1; b = 2; c = -15.8;
Δ = b2-4ac
Δ = 22-4·1·(-15.8)
Δ = 67.2
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(2)-\sqrt{67.2}}{2*1}=\frac{-2-\sqrt{67.2}}{2}
$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(2)+\sqrt{67.2}}{2*1}=\frac{-2+\sqrt{67.2}}{2}
$