-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

-1x^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}
$