化简求值:3a²-2[
解:
3a²-2[2ab²-(2ab-3a²b)+ab]+3ab²
原式=3a²-2[2ab²-2ab+3a²b+ab]+3ab²
=3a²-[4ab²-4ab+6a²b+2ab]+3ab²
=3a²+4ab²+4ab-6a²b-2ab+3ab²
=(4ab²+3ab²)+(4ab-2ab)+6a²b+3a²
=7ab²+2ab+6a²b+3a²
当a=1/2、b...全部
解:
3a²-2[2ab²-(2ab-3a²b)+ab]+3ab²
原式=3a²-2[2ab²-2ab+3a²b+ab]+3ab²
=3a²-[4ab²-4ab+6a²b+2ab]+3ab²
=3a²+4ab²+4ab-6a²b-2ab+3ab²
=(4ab²+3ab²)+(4ab-2ab)+6a²b+3a²
=7ab²+2ab+6a²b+3a²
当a=1/2、b=2时,
那么7ab²+2ab+6a²b+3a²=19。
75(此答案仅供参考)。收起