Tuesday, 4 June 2019

algebra precalculus - Inequality fracbab+b+1+fraccbc+c+1+fracaac+a+1gefrac3mm2+m+1




Let m=(abc)13, where a,b,cR+. Then prove that



bab+b+1+cbc+c+1+aac+a+13mm2+m+1



In this inequality I first applied Titu's lemma ; then Rhs will come 9/(some terms) ; now to maximise the rhs I tried to minimise the denominator by applying AM-GM inequality.But then the reverse inequality is coming
Please help.


Answer



By Holder:
cycbab+b+1=1(abc1)2cyc(ab+b+1)1(m31)2(3a2b2c2+3abc+1)3=



=1(m1)2(m2+m+1)2(m2+m+1)3=1(m1)2m2+m+1=3mm2+m+1.

Done!


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