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    Hi, ive had a crack at solving this logarithm but it has stumped me.

    Can you please help ?

    Solve for x:
    log x +log(x +1)=log30 (the logs are log base 10)

    My progress:
    log x +log(x +1)=log30
    log(x*(x+1) =log30
    log(x²+1x) =log30

    not sure where to go from here:eek3:

    Many thanks for any assistance
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    You can say: x²+x = 30 and solve from there.
    And when you solve, make sure that x is positive, because otherwise log(x) doesn't exist.
    Good luck.
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    x^2 + x = 30

    Edit: Ninja'd by oliv3r x]
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    Thanks chaps, I got it solved with your help.

    x²+x-30=0
    (x+6)(x-5)=0 (factorise)
    x=+5 or x=-6
    But x cannot be negative "because otherwise log(x) dosen't exist" (TY oliv3r)
    Therefore x = +5
    The answer in the book agrees.
 
 
 
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Updated: January 23, 2010
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