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  • Jul 26, 2011, 11:15 AM
    skbhatta49
    hard mathematics? Algebra
    2^x=x^2
    2 to the power X equals x to the power 2
    I have found a solution i.e 2 instantly but I found many answers so I operated by log which confused me
  • Jul 26, 2011, 12:20 PM
    ebaines
    1 Attachment(s)

    I'm not sure how you found "many answers" - I believe there are 3.

    For positive values of x you can do this:



    If you plot you'll see that f(x) equals at only two points, those being x = 2 and x=4. To prove that there are the only two solutions - if you find the derivative of this function you'll see that it equals zero only at x = e, so there can be at most two points where it equals . Hence there are only two solutions for positive values of x.

    For negative values of x we can let y = -x, and then a similar approach yields



    which has a solution at around y = 0.7667, so x = -0.7667 is the third solution. As a check - below is a plot of and and you can see the three points where the functions cross.

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