∵|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

．