已知A-2B=7a²-7ab,且B= -4a²+6ab+7(1)求A等于多少?(2)若|a+1|+(b-2)的2次方=0,求A的值
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![已知A-2B=7a²-7ab,且B= -4a²+6ab+7(1)求A等于多少?(2)若|a+1|+(b-2)的2次方=0,求A的值](/uploads/image/z/445123-19-3.jpg?t=%E5%B7%B2%E7%9F%A5A-2B%3D7a%26%23178%3B-7ab%2C%E4%B8%94B%3D+-4a%26%23178%3B%2B6ab%2B7%EF%BC%881%EF%BC%89%E6%B1%82A%E7%AD%89%E4%BA%8E%E5%A4%9A%E5%B0%91%3F%EF%BC%882%EF%BC%89%E8%8B%A5%7Ca%2B1%7C%2B%28b-2%29%E7%9A%842%E6%AC%A1%E6%96%B9%3D0%2C%E6%B1%82A%E7%9A%84%E5%80%BC)
已知A-2B=7a²-7ab,且B= -4a²+6ab+7(1)求A等于多少?(2)若|a+1|+(b-2)的2次方=0,求A的值
已知A-2B=7a²-7ab,且B= -4a²+6ab+7
(1)求A等于多少?(2)若|a+1|+(b-2)的2次方=0,求A的值
已知A-2B=7a²-7ab,且B= -4a²+6ab+7(1)求A等于多少?(2)若|a+1|+(b-2)的2次方=0,求A的值
A=7a²-7ab+2B
=7a²-7ab+2(-4a²+6ab+7)
=7a²-7ab-8a²+12ab+14
=-a²+5ab+14
|a+1|+(b-2)²=0
a+1=0 a=-1
b-2=0 b=2
A=-a²+5ab+14=-(-1)²-5X1X2+14=-1-10+14=3