I would have done that slightly differently. From

, add

to both sides to get

. Squaring both sides of that you get

. You still have the square root form the "cross term" but since you don't have both square roots on the same side, it's a little simpler. That can be reduced, by canceling the "x" terms on both sides and canceling the "-4" and "4", to

which reduces to

. Now square both sides again to get x- 4= 4.

Notice that while e^(i*pi)'s equation

**looks** like a quadratic, it is not be cause the [itex]x^2[/itex] terms on each side will cancel.