A:C3H6、C4H6O2
B:C2H6、C2H6O
C:C2H2、C6H6
D:C3H6O、C3H8O
句型转换
已知A=1x+1,B=x-1x2+2x-1,求A与B的差;当x≠﹣1时,比较A与B的大小.