-a(a²-2ab)-b(ab+2a²-b²)
= -a³+2a²b-ab²-2a²b+b³
= -a³-ab²+b³
= -2³-2×(1/2)²+(1/2)³
= -8-1/2+1/8
= -67/8對不起哈。少打了。應(yīng)該是-a(a²-2ab-b²)-b(ab+2a²-b²),其中a=2,b=1/2a=2,b=1/2-a(a²-2ab-b²)-b(ab+2a²-b²)= -a³+2a²b+ab²-ab²-2a²b+b³= -a³+b³= -2³+(1/2)³= -8+1/8= -63/8