Question

3a²b－［2a²－（ab²－3a²b）－4ab²］，其中｜a｜=2，b=2分之1，且ab＜0

Answer 1

先化简再求值: 3a²b-[2a²b-(2ab-a²b)-4a²]-ab =3a²b-[2a²b-2ab+a²b-4a²]-ab
=3a²b-[3a²b-2ab-4a²]-ab
=3a²b-3a²b+2ab+4a²-ab =ab+4a² 其中a=-3,b=-2
=(-3...

2.....解:(2a³-3a²-2ab²)-(a³-2ab²-b³)+(3a²b-a³-b³)=(2a³-a³-a³)-3a²+(-2ab²+2ab²)+3a²b-b³+b³=-3a²+3a²b=3a²(b-1)当a=1/2和a=-1/2时a²=1/4所以2个结...

3.......a=二分之一
b=三分之一
5(3a²b-ab²)-(ab²+3a²b) =15a²b-5ab²-ab²-3a²b =12a²b-6ab²
=6ab(2a-b) =6×1/2×1/3×(1-1/3)
=2/3