-28x(x+2)=0

Solution for -28x(x+2)=0 equation:

-28x(x+2)=0

We multiply parentheses

-28x^2-56x=0

a = -28; b = -56; c = 0;
Δ = b2-4ac
Δ = -562-4·(-28)·0
Δ = 3136
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{3136}=56$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-56)-56}{2*-28}=\frac{0}{-56}
=0
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-56)+56}{2*-28}=\frac{112}{-56}
=-2
$