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Math Help - Logarithms Questions helpppp~

  1. #1
    Junior Member
    Joined
    Sep 2008
    Posts
    34

    Logarithms Questions helpppp~

    Back with more Qs^^

    without calculator
    solve for x :

    logx = 3loga - logb +logc the answer is a^3c/b

    i canceled all the logs and got x =a^3-b+c than i got stuck

    simplify:
    4^log2 3

    i got to 3=2X than i got stuck the answer is 9... 3/2 can't get 9..

    whats the value of X :
    logx 8=3/4

    32=3^x stuck


    how can a square root b/c^2 = loga+1/2logb-2logc ?( can't find the root key on the keyboard>.<)

    ty
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  2. #2
    MHF Contributor
    Joined
    Sep 2008
    From
    West Malaysia
    Posts
    1,261

    Re :

    Quote Originally Posted by hovermet View Post
    Back with more Qs^^

    without calculator
    solve for x :

    logx = 3loga - logb +logc the answer is a^3c/b

    i canceled all the logs and got x =a^3-b+c than i got stuck

    simplify:
    4^log2 3

    i got to 3=2X than i got stuck the answer is 9... 3/2 can't get 9..

    whats the value of X :
    logx 8=3/4

    32=3^x stuck


    how can a square root b/c^2 = loga+1/2logb-2logc ?( can't find the root key on the keyboard>.<)

    ty

    (1) lgx=3lga-lgb+lgc , just apply the laws of logarithms

    lgx=lg[(a^3)(1/b)(c)]

    lgx=lg(\frac{ca^3}{b})
    then cancel logs from both sides .

    (2) 4^{log_23}

    =2^{2log_23}

    =2^{log_29}
    Do you know that a^{log_ax}=x

    (3) log_x8=3/4

    Try to convert it to index form and solve for X .
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  3. #3
    Junior Member
    Joined
    Sep 2008
    Posts
    34
    tyyy

    i didnt know that u can multiply the 3^2 and that formula >.<

    for number 3) whats that index form? is it the exponential form?

    x^3/4 =8
    3/4logx=8
    3logx=32


    stuck again the answer is 16

    4)
    how can "A"root b/c^2 = loga+1/2logb-2logc?

    got a few more

    5)given log80 = a which of the following is an expression for log2 in terms of a

    answer is a-1/3 (why)

    6) solve log2 x=log4 x^2
    answer is all real numbers(why)

    7) solve 1/log2 x + 1/log8 x =2
    helpp


    Can anyone also tell me the difference between evaluate and solve?
    solve is to solve for x but i dont know what evaluate is really looking for ty
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