Solve by using square root principle

[ (x+1)/2 ]^2 - (x/2) = 2

Answer key: ±√7

I tried the following:

[ (x+1)/2 ]^2 - (x/2) = 2

(x^2/4) + (1/4) - (x/2) = 2

-bring the (1/4) to RHS

(x^2/4) - (x/2) = (7/4)

-LCD 4

x^2 - 2x = 7

I'm stuck now as I have a middle term (-2x), otherwise the square root principle would work out nice. How to solve this using the square root principle?

Thanks.