2c^2+4c-84=4

Solution for 2c^2+4c-84=4 equation:

2c^2+4c-84=4

We move all terms to the left:

2c^2+4c-84-(4)=0

We add all the numbers together, and all the variables

2c^2+4c-88=0

a = 2; b = 4; c = -88;
Δ = b2-4ac
Δ = 42-4·2·(-88)
Δ = 720
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{720}=\sqrt{144*5}=\sqrt{144}*\sqrt{5}=12\sqrt{5}$
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(4)-12\sqrt{5}}{2*2}=\frac{-4-12\sqrt{5}}{4}
$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(4)+12\sqrt{5}}{2*2}=\frac{-4+12\sqrt{5}}{4}
$