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Math Help - yay logarithms. >:p

  1. #1
    Newbie veronica mars's Avatar
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    yay logarithms. >:p

    ok. i have done these before, but no one can explain 2 me how to solve a fricken logarithmic equation. so if you guys could help me, it would be AMAZING

    ok here it is:

    Solve each logarithmic equation.

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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by veronica mars View Post
    ok. i have done these before, but no one can explain 2 me how to solve a fricken logarithmic equation. so if you guys could help me, it would be AMAZING

    ok here it is:

    Solve each logarithmic equation.

    following the laws of logarithms:

    x = \log_5 \frac 1{625} \implies 5^x = \frac 1{625}

    can you continue?
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  3. #3
    Newbie veronica mars's Avatar
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    Quote Originally Posted by Jhevon View Post
    following the laws of logarithms:

    x = \log_5 \frac 1{625} \implies 5^x = \frac 1{625}

    can you continue?
    no that is where i am stuck
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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by veronica mars View Post
    no that is where i am stuck
    the trick is to express both sides in the same base. do you know what 625 is, if you write it as 5 to some power?
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  5. #5
    Newbie veronica mars's Avatar
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    Quote Originally Posted by Jhevon View Post
    the trick is to express both sides in the same base. do you know what 625 is, if you write it as 5 to some power?
    no that is what i can't find. that is where i am stuck. i know that i have to get the same base, but no matter how many times i do it, i cannot figure it out. i have looked in notes, and in examples, and i dont know what could be put to the fifth to equal 625. the only thing i know is what you already said, and that the answer is -4 (i looked in the back of the book)
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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by veronica mars View Post
    no that is what i can't find. that is where i am stuck. i know that i have to get the same base, but no matter how many times i do it, i cannot figure it out. i have looked in notes, and in examples, and i dont know what could be put to the fifth to equal 625. the only thing i know is what you already said, and that the answer is -4 (i looked in the back of the book)
    how could you not figure it out. just keep multiplying till you get it.

    5*5 = 5^2 = 25

    5*5*5 = 5^3 = 125

    5*5*5*5 = 5^4 = 625 ..........Bingo!

    thus we have: 5^x = \frac 1{5^4}

    \Rightarrow 5^x = 5^{-4} .....................since \frac 1{x^a} = x^{-a}

    equate the powers, since if the bases are the same, the powers must be the same to have equality

    thus, x = -4

    as desired
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  7. #7
    MHF Contributor Mathstud28's Avatar
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    Quote Originally Posted by veronica mars View Post
    ok. i have done these before, but no one can explain 2 me how to solve a fricken logarithmic equation. so if you guys could help me, it would be AMAZING

    ok here it is:

    Solve each logarithmic equation.

    log_{5}\bigg(\frac{1}{625}\bigg)=\log_{5}(5^{-4})=-4

    I only answered becasue I could not find your original post
    Last edited by Mathstud28; April 22nd 2008 at 05:45 PM.
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  8. #8
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by veronica mars View Post
    ok. sorry i didnt know that we werent allowed to not swear and i wasnt sure which catagory my question fell under. this is because i would like to be answered as soon as possible (urgent math help) but if there are other people whose situation is more urgent than mine, i would like to have my question answered in the less urgent area (trigonometry help)

    i hope you understand where im coming from
    it is ok. it doesn't matter too much. if you post in the wrong category, the mods can move your thread to the right one. don't worry about it, just don't do it again.

    and also, this site caters to math of all levels. so kids are often on here. we ask you to refrain from cursing for their sake.

    Quote Originally Posted by Mathstud28 View Post
    log_{5}\bigg(\frac{1}{625}\bigg)=\log_{5}(5^-4)=-4

    I only answered becasue I could not find your original post
    were that the case, you could have went to her profile and find the threads she created (as easy as clicking on her name). i already responded to her post. you did it a different way, so i guess it is not so bad.
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    If you want to talk go to one of those talk forums. I had to delete 18 useless posts not one of them having to do with math.
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