Saturday, October 4, 2008

Problem Of The Week 43

Find the number of real roots (x+1)^x=x^(x+1)

14 comments:

  1. No solution!But I couldn't find any method do prove it..

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  2. what is the method?

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  3. I took log to the base x of both sides and solved it for x.

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  4. But then x can't be -1. so it could be no solution.

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  5. there is a solution try again !

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  6. I tried constructing a graph for the equation. Infinite real roots?
    Totally confused with the question. @ Outtimed can you please explain the answer.

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  7. The graph is a straight line parallel to an axis

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  8. The value of x or if we think of it as values , will lie between 2 and 3 as for 2 or less than 2 one side of the equation becomes greater than the other and for 3 or greater than 3 , the other side of the equation becomes greater.

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  9. x comes to be the xth root of (1+1/x). Thus this forms an infinite series.

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  10. log(x+1)/(x+1)=logx/x

    take f(y)=logy/y
    plot the graph

    now check if you can find a solution or not

    hint: the graph does not rise or dip monotonously!

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  11. basically we get

    (1+1/n)^n =n
    so basically we get one root between 2 and 3 and later on as limit of left hand side is e when n approaches infinity.. so just one root..

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  12. plotting the graph for log y/y between y=2 to 4 we get a curve which first increases then decreases, the value is almost same for 2.3 and 3.3, around 0.157

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