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Funny Stuff ! (Posted on 2002-06-20) Difficulty: 4 of 5
Given:
   a,b,c >0 and a+b+c=1 ;
   P=(1/a)+(2/b)+(3/c);
1)Find the minimum value of P;
2)Does P have maximum value ?

  Submitted by vohonam    
Rating: 3.4286 (7 votes)
Solution: (Hide)
P*1 = (a+b+c)*(1/a+2/b+3/c); P*1=6+2a/b + 3a/c + b/a + 3b/c + c/a + 2c/b P=6+(2a/b+b/a)+(3a/c+c/a)+(3b/c+2c/b) Use Cauchy's inequality for each : we have : P >= 6+ 2*sqrt(2)+2*sqrt(3)+2*sqrt(6) "=" when a+b+c=1 and b=a*sqrt(2) c=a*sqrt(3) ===>we can solve for a,b,c No maximum value.

Comments: ( You must be logged in to post comments.)
  Subject Author Date
Some Thoughtsre(6): Puzzle AnswerK Sengupta2022-09-05 14:41:33
re(5): Puzzle AnswerSteven Lord2022-09-05 13:10:17
re(4): Puzzle AnswerK Sengupta2022-09-05 12:39:30
re(3): Puzzle AnswerSteven Lord2022-09-05 11:46:29
re(2): Puzzle AnswerK Sengupta2022-09-05 08:33:02
re: Puzzle AnswerSteven Lord2022-09-05 05:43:10
Puzzle AnswerK Sengupta2022-09-05 03:27:00
SolutionHard and grusome methodBon2004-08-06 04:38:33
re: Cauchy's inequality !friedlinguini2002-06-21 15:17:48
Some ThoughtsCauchy's inequality !vohonam2002-06-21 13:58:48
re: A better way to solve this !friedlinguini2002-06-21 12:44:15
SolutionA better way to solve this !vohonam2002-06-21 11:58:55
MINUM = WRONG MAXIMUM = INIFINITYquddous behrouzi2002-06-21 10:18:07
SolutionMINIMUM = 27 MAXIMUM = INIFINITYquddous behrouzi2002-06-21 10:07:53
Solutionre: Whatever happened to that textbook...?friedlinguini2002-06-21 06:00:04
Whatever happened to that textbook...?TomM2002-06-20 22:30:34
Oh WellTomM2002-06-20 20:47:41
re: solution (maybe)- Novohonam2002-06-20 20:29:52
Solutionsolution (maybe)TomM2002-06-20 20:09:57
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