The given equation does not have any real solutions.
-2 cannot be a solution since every radical is positive and Vx= +y only.
It it is highly important to see what values the variable can take before even attempting to solve the equation.
In this case, for instance, x >= 0 because it is on the right side of a radical equation and -4x-4 >= 0 because it is under the sign of the radical. The second one gives x <= -1, so the two multitudes do not intersect, hence there is no real solution.
-2 gives -2 = 2
Now, 16+36=c^2 does equal c=2√13 and c=-2√13, unless it is known for c that it is greater than zero, like when regarding a geometry problem.