第1个回答 2017-10-20
图解
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第2个回答 2017-10-20
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上面四种方法供你参考。
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证明不等式:a方+b方+1大于等于ab+a+b答:设I=a^2+b^2+1-(ab+a+b)=a^2+b^2-2ab+(ab-a-b+1)=(a-b)^2+(a-1)(b-1)如果a-1,b-1有一个为零,那么不等式显然成立.如果a-1,b-1同号,那么不等式也成立.如果a-1,b-1异号,由于a,b有对称性,不妨设a-1>0,b-1<0,假使a=b+c,则c>0.则(a-b)^2=c^2,(a-1...