First simplify and then evaluate: - (x2 + Y2) + [- 3xy - (x2-y2)], where x = - 1, y = 2

First simplify and then evaluate: - (x2 + Y2) + [- 3xy - (x2-y2)], where x = - 1, y = 2

The original formula = - x2-y2-3xy-x2 + y2 = - 2x2-3xy, when x = - 1, y = 2, the original formula = - 2 × (- 1) 2-3 × (- 1) × 2 = 4