4x²y-[6xy-2（3xy-2）-x²y]+1

=4x²y-[6xy-（6xy-4）-x²y]+1

=4x²y-（6xy-6xy+4-x²y）+1

=4x²y-（4-x²y）+1

=4x²y-4+x²y+1

=5x²y-3，

当x=-

1

2

，y=4时，原式=5x²y-3=5×(-

1

2

)2×4-3=5-3=2．