28a^2-84a-63=0

Solution for 28a^2-84a-63=0 equation:

28a^2-84a-63=0

a = 28; b = -84; c = -63;
Δ = b2-4ac
Δ = -842-4·28·(-63)
Δ = 14112
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{14112}=\sqrt{7056*2}=\sqrt{7056}*\sqrt{2}=84\sqrt{2}$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-84)-84\sqrt{2}}{2*28}=\frac{84-84\sqrt{2}}{56}
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-84)+84\sqrt{2}}{2*28}=\frac{84+84\sqrt{2}}{56}
$