已知:A+2B=7a²-7ab,且B=-4a²+6ab+71.求A等于多少?2.若丨a+1丨+(b-2)²=0,求A的值.

问题描述:

已知:A+2B=7a²-7ab,且B=-4a²+6ab+7
1.求A等于多少?
2.若丨a+1丨+(b-2)²=0,求A的值.

A+2B=7a²-7ab
B=-4a²+6ab+7
2B=-4a²+12ab+14
A=7a²-7ab-2B=7a²-7ab-(-4a²+12ab+14)
=7a²-7ab+4a²-12ab-14
=11a²-19ab-14