An Optimal Double Inequality for Means

نویسندگان

  • Wei-Mao Qian
  • Ning-Guo Zheng
  • Alberto Cabada
چکیده

For p ∈ R, the generalized logarithmic mean Lp a, b , arithmetic mean A a, b and geometric mean G a, b of two positive numbers a and b are defined by Lp a, b a, a b; Lp a, b a 1 − b 1 / p 1 a − b , p / 0, p / − 1, a/ b; Lp a, b 1/e b/a 1/ b−a , p 0, a/ b; Lp a, b b − a / ln b − lna , p −1, a/ b; A a, b a b /2 and G a, b √ ab, respectively. In this paper, we give an answer to the open problem: for α ∈ 0, 1 , what are the greatest value p and the least value q, such that the double inequality Lp a, b ≤ G a, b A1−α a, b ≤ Lq a, b holds for all a, b > 0?

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تاریخ انتشار 2010