Results 1 to 4 of 4

Thread: [SOLVED] need logarithm help

  1. #1
    Newbie
    Joined
    Mar 2010
    Posts
    21

    [SOLVED] need logarithm help

    hi i need help on solving these questions with all the log rules i'm confusing myself..

    1). 7^(x-2) = 1/2^(x-2)

    2). 10^(x^2+2x-8) = 1

    3). (1/4)^(x+2) * 32^(x-1) = 64^(x-2)

    i know i have to solve for x but i keep getting the wrong answers when i plug it into my graph and find the intersections for the answer.

    thanks!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member Anonymous1's Avatar
    Joined
    Nov 2009
    From
    Big Red, NY
    Posts
    517
    Thanks
    1
    For (1) do you mean $\displaystyle 7^{x-2}= \frac{1}{2^{x-2}}?$

    Then, $\displaystyle (x-2)\log(7) = (2-x)\log(2)$

    $\displaystyle => (x-2)=(2-x)\frac{\log(2)}{\log(7)}$

    Let $\displaystyle \frac{\log(2)}{\log(7)} = \alpha $

    and solve to find $\displaystyle x= 2$

    For (2) take the log of both sides:

    $\displaystyle \log_{10} (10^{(x^2+2x-8)}) = log_{10}(1)$

    $\displaystyle => x^2+2x-8 = \log_{10}(1)$

    $\displaystyle => x^2+2x-8-\log_{10}(1) = 0$

    Now use the quadratic equation to find your solutions. Where,

    $\displaystyle a= 1$
    $\displaystyle b= 2$
    $\displaystyle c= -(8+\log_{10}(1))$

    For (3) again take the log of both sides.

    $\displaystyle \log[(1/4)^{x+2}\times 32^{x-1}] = \log[64^{x-2}]$

    $\displaystyle => (x+2)\log(1/4)+(x-1)\log(32) = (x-2)\log(64)$

    $\displaystyle ...$
    Last edited by Anonymous1; Mar 17th 2010 at 06:48 PM.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Mar 2010
    Posts
    21
    wow thanks a lot! it really helped, i was really off with some of them
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Super Member Anonymous1's Avatar
    Joined
    Nov 2009
    From
    Big Red, NY
    Posts
    517
    Thanks
    1
    Logarithms with start to get intuitive, just keep practicing.

    Good luck,
    Anonymous
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. [SOLVED] Help with logarithm
    Posted in the Algebra Forum
    Replies: 2
    Last Post: Apr 7th 2010, 10:26 PM
  2. [SOLVED] Logarithm with different base
    Posted in the Algebra Forum
    Replies: 5
    Last Post: Aug 13th 2009, 10:40 PM
  3. [SOLVED] Natural Logarithm
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: Feb 28th 2009, 08:23 AM
  4. [SOLVED] Logarithm Problem
    Posted in the Pre-Calculus Forum
    Replies: 8
    Last Post: Feb 4th 2009, 06:31 PM
  5. [SOLVED] HW2-Qst 9-Logarithm question
    Posted in the Algebra Forum
    Replies: 2
    Last Post: Aug 20th 2008, 01:51 PM

Search Tags


/mathhelpforum @mathhelpforum