1. The problem statement, all variables and given/known data Given x^2 - xy + y^2 = 4(x+y-4) where x, y both are real then the number of pairs (x, y) satisfying the equation will be (A) Only one (B) Two (C) Three (D) No pair 2. Relevant equations 3. The attempt at a solution The equation can be written as (x-2)^2 + (y-2)^2 + 8 = xy on opening the brackets and completing the square. Beyond this, I really don't know what to do. Hit and trial doesn't seem to work very well either.