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Math Help - Need quick help with logarithms

  1. #1
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    Need quick help with logarithms

    I am currently helping someone with their online school work. If they do not get it done within the next couple of hours, they will be denied their high school diploma. They were failed due to absences, and the online class covers much more than they were required to go over in public school.

    1. if logb3=0.23 and logb8 = 0.71, find logb24
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  2. #2
    MHF Contributor MarkFL's Avatar
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    Re: Need quick help with logarithms

    Hint: use the property of logs:

    \log_b(x)+\log_b(y)=\log_b(xy)
    Thanks from Chace
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  3. #3
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    Re: Need quick help with logarithms

    So I would just do (.23)x(.71) and get .1633?
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  4. #4
    MHF Contributor MarkFL's Avatar
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    Re: Need quick help with logarithms

    No, you want to add:

    \log_b(3)+\log_b(8)=\log_b(24)

    Now, substitute the given values for the log functions on the left.
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  5. #5
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    Re: Need quick help with logarithms

    Oh! Wow, that was pretty silly of me. Thanks!

    Would you mind helping explain how to expand and condense logarithmic equations?

    For instance: log2((7(p-3))6/q2r)
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  6. #6
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    Re: Need quick help with logarithms

    Could some of you please go over to my question and help me out? I need to turn these 3 questions in very soon. PLEASE HELP!
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  7. #7
    MHF Contributor MarkFL's Avatar
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    Re: Need quick help with logarithms

    Quote Originally Posted by Chace View Post
    Oh! Wow, that was pretty silly of me. Thanks!

    Would you mind helping explain how to expand and condense logarithmic equations?

    For instance: log2((7(p-3))6/q2r)
    There are some properties you may use:

    \log_a\left(b^c\right)=c\cdot\log_a(b)

    \log_a(bc)=\log_a(b)+\log_a(c)

    \log_a\left(\frac{b}{c}\right)=\log_a(b)-\log_a(c)

    Do you see how to apply these to expand the expression you posted?
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  8. #8
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    Re: Need quick help with logarithms

    Need quick help with logarithms-log-problem.gif

    Here is a better image of the problem I was referring to.

    Would it be:

    6log27+6log2(p-3)-2log2q+log2r?
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  9. #9
    MHF Contributor MarkFL's Avatar
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    Re: Need quick help with logarithms

    Very close, but the last term needs a minus sign in front as r was in the denominator.
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  10. #10
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    Re: Need quick help with logarithms

    Need quick help with logarithms-log-problem-1.jpg

    Here's another problem!

    I am inclined to go with A. Thoughts?
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  11. #11
    MHF Contributor MarkFL's Avatar
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    Re: Need quick help with logarithms

    It's not A since the exponent 3 was not on the 18...
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  12. #12
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    Re: Need quick help with logarithms

    Ah, too true. I feel as if B is the correct answer.

    The reason I say this is because in C, the coefficient "2" should also apply to the log9, correct?

    Also: in D, I don't believe the 4 corresponds to everything that it should.
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  13. #13
    MHF Contributor MarkFL's Avatar
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    Re: Need quick help with logarithms

    Yes, your reasoning is correct.
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