(1)A-2B=2x²+3xy+2y-1-2( x²-xy+x-1/2)
=2x²+3xy+2y-1-2x²+2xy-2x+1
=5xy+2y-2x,
当x=y=-2时,
A-2B=5xy+2y-2x
=5×(-2)×(-2)+2×(-2)-2×(-2)
=20;
(2)由(1)可知A-2B=5xy+2y-2x=(5y-2)x+2y,
若A-2B的值与x的取值无关,则5y-2=0,
解得 y=2/5.
(1)A-2B=2x²+3xy+2y-1-2( x²-xy+x-1/2)
=2x²+3xy+2y-1-2x²+2xy-2x+1
=5xy+2y-2x,
当x=y=-2时,
A-2B=5xy+2y-2x
=5×(-2)×(-2)+2×(-2)-2×(-2)
=20;
(2)由(1)可知A-2B=5xy+2y-2x=(5y-2)x+2y,
若A-2B的值与x的取值无关,则5y-2=0,
解得 y=2/5.