先化简后求值:【(ab+3)(ab-3)-3(a²b²-3)】÷(ab),其中a=-½,b=1/3

问题描述:

先化简后求值:【(ab+3)(ab-3)-3(a²b²-3)】÷(ab),其中a=-½,b=1/3

原式=[a²b²-9-(3a²b²-9)]÷(ab)
=(a²b²-9-3a²b²+9)÷(ab)
=(-2a²b²)÷(ab)
=-2ab
=-2×(-1/2)×(1/3)
=1/3