April 14, 2007

Math World No.007

最近算不等式算得真快樂啊~ ^^


設a、b為正數,0<x、y、z<a/b,且x+y+z=1,求證:
x/(a-bx)+y/(a-by)+z/(a-bz)≧3a-b
Hint:想辦法用柯西湊出來吧~ (請反白)
(《數學通報》數學問題668題)

設a、b、c、d為非負實數,且ab+bc+cd+da=1,求證:
a3/(b + c + d) + b3/(a + c + d) + c3/(a + b + d) + d3/(a + b + c) ≥ 1/3
Hint:同上~再加個算幾~ ^^ (請反白)
(第31屆(1990)IMO預選題)

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