n^2+8n=140

Solution for n^2+8n=140 equation:

n^2+8n=140

We move all terms to the left:

n^2+8n-(140)=0

a = 1; b = 8; c = -140;
Δ = b2-4ac
Δ = 82-4·1·(-140)
Δ = 624
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:

$\sqrt{\Delta}=\sqrt{624}=\sqrt{16*39}=\sqrt{16}*\sqrt{39}=4\sqrt{39}$
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(8)-4\sqrt{39}}{2*1}=\frac{-8-4\sqrt{39}}{2}
$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(8)+4\sqrt{39}}{2*1}=\frac{-8+4\sqrt{39}}{2}
$