4x²y-［6xy-3（4xy-2）-x²y］+1 x=2 y=负二分之一

4x²y-［6xy-3（4xy-2）-x²y］+1 x=2 y=负二分之一
4x²y-［6xy-3（4xy-2）-x²y］+1 x=2 y=负二分之一

4x²y-［6xy-3（4xy-2）-x²y］+1 x=2 y=负二分之一
原式=4x²y-(6xy-12xy+6-x²y)+1
=4x²y-6xy+12xy-6+x²y+1
=(4x²y+x²y)+(-6xy+12xy)+(-6+1)
=5x²y+6xy-5
当x=2,y=-1/2时
原式=5×2²×(-1/2)+6×2×(-1/2)-5
=5×4×(-1/2)-6-5
=-10-6-5
=-21

=4x2y-(6xy-12xy+6-x2y)+1
=4x2y+6xy-6+x2y+1
=4x2y+6xy+x2y-5
=8+6+2-5
=11