28m2+6m-7=0

Solution for 28m2+6m-7=0 equation:

28m^2+6m-7=0

a = 28; b = 6; c = -7;
Δ = b2-4ac
Δ = 62-4·28·(-7)
Δ = 820
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$m_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$m_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{820}=\sqrt{4*205}=\sqrt{4}*\sqrt{205}=2\sqrt{205}$
$m_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(6)-2\sqrt{205}}{2*28}=\frac{-6-2\sqrt{205}}{56}
$
$m_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(6)+2\sqrt{205}}{2*28}=\frac{-6+2\sqrt{205}}{56}
$