求当a=-二分之一,b=1时,代数式:2a²b-[2ab²-2(a²b+2ab²)]的值.

问题描述:

求当a=-二分之一,b=1时,代数式:2a²b-[2ab²-2(a²b+2ab²)]的值.

2a²b-[2ab²-2(a²b+2ab²)]
=2a²b-[2ab²-2a²b-4ab²]
=2a²b-2ab²+2a²b+4ab²
=4a²b+2ab²