x2-300x=6400

Solution for x2-300x=6400 equation:

x2-300x=6400

We move all terms to the left:

x2-300x-(6400)=0

We add all the numbers together, and all the variables

x^2-300x-6400=0

a = 1; b = -300; c = -6400;
Δ = b2-4ac
Δ = -3002-4·1·(-6400)
Δ = 115600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{115600}=340$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-300)-340}{2*1}=\frac{-40}{2}
=-20
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-300)+340}{2*1}=\frac{640}{2}
=320
$