cho a,b >0 thỏa mãn $a^{3}+b^{3}=a^{5}+b^{5}.CMR$ $a^{2}+b^{2}\leq ab+1$
cho a,b >0 thỏa mãn $a^{3}+b^{3}=a^{5}+b^{5}.CMR$ $a^{2}+b^{2}\leq ab+1$
Started By Mori Ran, 12-05-2013 - 15:57
#1
Posted 12-05-2013 - 15:57
#2
Posted 12-05-2013 - 16:38
cho a,b >0 thỏa mãn $a^{3}+b^{3}=a^{5}+b^{5}.CMR$ $a^{2}+b^{2}\leq ab+1$
BĐT cần chứng minh $\Leftrightarrow a^{2}-ab+b^{2}\leq 1$
$\Leftrightarrow (a^{3}+b^{3})(a^{2}-ab+b^{2})\leq a^{5}+b^{5}$
$\Leftrightarrow a^{4}b+ab^{4}\geq a^{3}b^{2}+a^{2}b^{3}$
$\Leftrightarrow ab(a+b)(a-b)^{2}\geq 0$ (Đúng)
Vậy ta có đpcm.
Edited by Oral1020, 12-05-2013 - 16:59.
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ONG NGỰA 97.
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