Question

[Đỗ Mai Gia Linh]

Tính:

a)(3x²-2xy+y²)+(x²-xy+2y²)-(4x²-y²)

b)(x²-y²+2xy)-(x²+xy+2y²)+(4xy-1)

c) Tìm đa thức M biết: M-(2xy-4y)²=5xy+x²-7y²

Answer 1

[Nguyễn Mai]

a, (3x²-2xy+y²) + (x²-xy+2y²) - (4x²-y²)

= 3x²-2xy+y²+x²-xy+2y²-4x²+y²

= 4y²-3xy

b, = x²-y²+2xy-x²-xy-2y²+4xy-1

= -3y²+5xy

c, M=5xy+x²-7y²+(2xy-4y)² = 5xy+x²-7y²+4x²y²-16xy²+16y² = 5xy+x²+9y²+4x²y²-16xy²