4x2-12x-28=0

Solution for 4x2-12x-28=0 equation:

4x^2-12x-28=0

a = 4; b = -12; c = -28;
Δ = b2-4ac
Δ = -122-4·4·(-28)
Δ = 592
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:

$\sqrt{\Delta}=\sqrt{592}=\sqrt{16*37}=\sqrt{16}*\sqrt{37}=4\sqrt{37}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-12)-4\sqrt{37}}{2*4}=\frac{12-4\sqrt{37}}{8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-12)+4\sqrt{37}}{2*4}=\frac{12+4\sqrt{37}}{8}
$