4x²y-[6xy-2（4xy-2）-x²y]+1

=4x²y-6xy+8xy-4+x²y+1

=5x²y+2xy-3，

当x=-

1

2

，y=4时，原式=5×（-

1

2

）²×4+2×（-

1

2

）×4-3=-2．