28x2-56x-84=0

Solution for 28x2-56x-84=0 equation:

28x^2-56x-84=0

a = 28; b = -56; c = -84;
Δ = b2-4ac
Δ = -562-4·28·(-84)
Δ = 12544
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{12544}=112$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-56)-112}{2*28}=\frac{-56}{56}
=-1
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-56)+112}{2*28}=\frac{168}{56}
=3
$