X2-120x-1400=0

Solution for X2-120x-1400=0 equation:

X2-120X-1400=0

We add all the numbers together, and all the variables

X^2-120X-1400=0

a = 1; b = -120; c = -1400;
Δ = b2-4ac
Δ = -1202-4·1·(-1400)
Δ = 20000
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{20000}=\sqrt{10000*2}=\sqrt{10000}*\sqrt{2}=100\sqrt{2}$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-120)-100\sqrt{2}}{2*1}=\frac{120-100\sqrt{2}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-120)+100\sqrt{2}}{2*1}=\frac{120+100\sqrt{2}}{2}
$