1/2a²-[1/2（ab-a²)+4ab]-1/2ab 怎么解

1/2a²-[1/2（ab-a²)+4ab]-1/2ab 怎么解
1/2a²-[1/2（ab-a²)+4ab]-1/2ab 怎么解

1/2a²-[1/2（ab-a²)+4ab]-1/2ab 怎么解
原式=1/2a²-(1/2ab-1/2a²+4ab)-1/2ab
=1/2a²-1/2ab+1/2a²-4ab-1/2ab
=a²-5ab