已知A-2B=7a²-7ab,B=-4a²+6ab+7 (1)求A (2)若|a+1|=0,(b-
已知A-2B=7a²-7ab,B=-4a²+6ab+7
(1)求A
(2)若|a+1|=0,(b-2²)=0,A的值