14x(2x-4)=28

Solution for 14x(2x-4)=28 equation:

14x(2x-4)=28

We move all terms to the left:

14x(2x-4)-(28)=0

We multiply parentheses

28x^2-56x-28=0

a = 28; b = -56; c = -28;
Δ = b2-4ac
Δ = -562-4·28·(-28)
Δ = 6272
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:

$\sqrt{\Delta}=\sqrt{6272}=\sqrt{3136*2}=\sqrt{3136}*\sqrt{2}=56\sqrt{2}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-56)-56\sqrt{2}}{2*28}=\frac{56-56\sqrt{2}}{56}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-56)+56\sqrt{2}}{2*28}=\frac{56+56\sqrt{2}}{56}
$