2 ĐIỂMM =( 2X2 – 3X – Y2 + 2Y + 6XY + 5) + (- X2 + 3Y – 5X +Y +3XY +1)...
Câu 3: 2 điểm
M =( 2x
2
– 3x – y
2
+ 2y + 6xy + 5) + (- x
2
+ 3y – 5x +y +3xy +1) – (4xy +3x
2
+ 4y
2
–
5x – 3y + 6)
= 2x
2
– 3x – y
2
+ 2y + 6xy + 5 - x
2
+ 3y– 5x +y +3xy +1- 4xy -3x
2
- 4y
2
+ 5x +3y – 6
= - 2x
2
- 3x + 5xy + 9y
Thay x = 1; y = -1 thì M = -2 – 3 – 5 – 9 = - 19