x(x+100)=5600

Solution for x(x+100)=5600 equation:

x(x+100)=5600

We move all terms to the left:

x(x+100)-(5600)=0

We multiply parentheses

x^2+100x-5600=0

a = 1; b = 100; c = -5600;
Δ = b2-4ac
Δ = 1002-4·1·(-5600)
Δ = 32400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{32400}=180$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(100)-180}{2*1}=\frac{-280}{2}
=-140
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(100)+180}{2*1}=\frac{80}{2}
=40
$