∵
m-n=4
mn=-1
∴
-2mn+2m+3n-3mn-2n+2m-m-4n-mn
=-6mn+3m-3n
=-6mn+3(m-n)
=6+3*4
=6+12
=18
(2)(5xy-3x²+3)+2y²-2xy+2x²-3xy-2y+x²-3
=5xy-3x²+3+2y²-5xy+3x²-3-2y
=2y²-2y
所以和x取值无关的
∵
m-n=4
mn=-1
∴
-2mn+2m+3n-3mn-2n+2m-m-4n-mn
=-6mn+3m-3n
=-6mn+3(m-n)
=6+3*4
=6+12
=18
(2)(5xy-3x²+3)+2y²-2xy+2x²-3xy-2y+x²-3
=5xy-3x²+3+2y²-5xy+3x²-3-2y
=2y²-2y
所以和x取值无关的