∵|a-

1

2

|+（b+2）²=0，
∴a=

1

2

，b=-2，
则a³-3a²b+4ab²-2b³
=

1

8

-3×

1

4

×（-2）+4×

1

2

×（-2）²-2×（-2）³
=

1

8

+

3

2

+

1

2

+16
=18

1

8

．