已知A-2B=7a²-7ab,且B=-4a²+6ab+7.(1)求A等于多少?(2)若a+1已知A-2B=7a²-7ab,且B=-4a²+6ab+7.(1)求A等于多少?(2)若a+1的绝对值+(b-2)²=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已知A-2B=7a²-7ab,且B=-4a²+6ab+7.(1)求A等于多少?(2)若a+1的绝对值+(b-2)²=0,求A的值.](/uploads/image/z/765124-52-4.jpg?t=%E5%B7%B2%E7%9F%A5A-2B%3D7a%26%23178%3B-7ab%2C%E4%B8%94B%3D-4a%26%23178%3B%EF%BC%8B6ab%EF%BC%8B7.%281%29%E6%B1%82A%E7%AD%89%E4%BA%8E%E5%A4%9A%E5%B0%91%3F%282%29%E8%8B%A5a%EF%BC%8B1%E5%B7%B2%E7%9F%A5A-2B%3D7a%26%23178%3B-7ab%2C%E4%B8%94B%3D-4a%26%23178%3B%EF%BC%8B6ab%EF%BC%8B7.%281%29%E6%B1%82A%E7%AD%89%E4%BA%8E%E5%A4%9A%E5%B0%91%3F%282%29%E8%8B%A5a%EF%BC%8B1%E7%9A%84%E7%BB%9D%E5%AF%B9%E5%80%BC%EF%BC%8B%28b-2%29%26%23178%3B%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已知A-2B=7a²-7ab,且B=-4a²+6ab+7.(1)求A等于多少?(2)若a+1的绝对值+(b-2)²=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
已知A-2B=7a²-7ab,且B=-4a²+6ab+7.
(1)求A等于多少?
(2)若a+1的绝对值+(b-2)²=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已知A-2B=7a²-7ab,且B=-4a²+6ab+7.(1)求A等于多少?(2)若a+1的绝对值+(b-2)²=0,求A的值.
(1)A=7a²-7ab+2B=7a²-7ab+2(-4a²+6ab+7)=-a²+5ab+14;
(2)若|a+1|+(b-2)²=0,则|a+1|=-(b-2)²,而|a+1|≧0,(b-2)²≧0,可见,只有当|a+1|、(b-2)²都为0 时,|a+1|=-(b-2)²才能成立,故|a+1|=0,a=-1.
代入算一下就行了