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Among all pairs of number whose sum is 22, find a pair whose productg is as large as possible. What is the maximum product?

 Oct 28, 2015

Best Answer 

 #1
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\(\mbox{We want to maximize }x y \mbox{ subject to }x+y=22\\ y=22-x \\ x y = (22-x)x = 22x - x^2 = -(x^2-22x) = \\ -((x-11)^2-121) = 121-(x-11)^2 \\ \mbox{This has a maximum value of }121 \mbox{ at }x=y=11\)

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 Oct 28, 2015
 #1
avatar+6251 
+10
Best Answer

\(\mbox{We want to maximize }x y \mbox{ subject to }x+y=22\\ y=22-x \\ x y = (22-x)x = 22x - x^2 = -(x^2-22x) = \\ -((x-11)^2-121) = 121-(x-11)^2 \\ \mbox{This has a maximum value of }121 \mbox{ at }x=y=11\)

Rom Oct 28, 2015
 #2
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Well, I don't know what to make of your puzzle!!!!. To me: 21! X 1!=5.1 X 10^19, if that's acceptable to you? I know that 22/2=11 X 11=121, but that's peanuts compared to the number before it!!!.

 Oct 28, 2015

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