先化简,再求值:5(3a²b-ab²)-4(-ab²+3a²b)其中a=1/2,b=-1/3

先化简,再求值:5(3a²b-ab²)-4(-ab²+3a²b)其中a=1/2,b=-1/3
先化简,再求值:5(3a²b-ab²)-4(-ab²+3a²b)其中a=1/2,b=-1/3

先化简,再求值:5(3a²b-ab²)-4(-ab²+3a²b)其中a=1/2,b=-1/3
解
5(3a²b-ab²)-4(-ab²+3a²b)
=(15a²b-12a²b)+(-5ab²+4ab²)
=3a²b-ab²
=ab(3a-b)
=1/2×(-1/3)(3×1/2+1/3)
=-1/6×(3/2+1/3)
=-1/6×11/6
=-11/36