Quantcast

Got Homework?

Connect with other students for help. It's a free community.

  • across
    MIT Grad Student
    Online now
  • laura*
    Helped 1,000 students
    Online now
  • Hero
    College Math Guru
    Online now

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

pratu043

Can someone please explain how to solve a log equation with an example.

  • one year ago
  • one year ago

  • This Question is Closed
  1. dpaInc
    Best Response
    You've already chosen the best response.
    Medals 0

    how 'bout u pick an example....

    • one year ago
  2. dpaInc
    Best Response
    You've already chosen the best response.
    Medals 0

    otherwise i'll choose the easiest...:)

    • one year ago
  3. pratu043
    Best Response
    You've already chosen the best response.
    Medals 1

    OK ... \[5^{x - 3} . 3^{2x-8} = 225\]

    • one year ago
  4. pratu043
    Best Response
    You've already chosen the best response.
    Medals 1

    How to solve this using log? I'm new so I have no idea.

    • one year ago
  5. pratu043
    Best Response
    You've already chosen the best response.
    Medals 1

    I mean new to log.

    • one year ago
  6. pratu043
    Best Response
    You've already chosen the best response.
    Medals 1

    pls help.

    • one year ago
  7. lgbasallote
    Best Response
    You've already chosen the best response.
    Medals 0

    welcome to logarithms!

    • one year ago
  8. pratu043
    Best Response
    You've already chosen the best response.
    Medals 1

    Yeah thanks!

    • one year ago
  9. waterineyes
    Best Response
    You've already chosen the best response.
    Medals 3

    I guess you can solve this without using Logs..

    • one year ago
  10. pratu043
    Best Response
    You've already chosen the best response.
    Medals 1

    But I want to know how to do it with log.

    • one year ago
  11. waterineyes
    Best Response
    You've already chosen the best response.
    Medals 3

    Okay then all here will explain you how to do this...

    • one year ago
  12. moha_10
    Best Response
    You've already chosen the best response.
    Medals 0

    15^(x-3)+(2x-8)=225 now we take ln (3x-11)15= ln225

    • one year ago
  13. pratu043
    Best Response
    You've already chosen the best response.
    Medals 1

    What is In? And how did you get 15^(x-3)+(2x-8)=225?

    • one year ago
  14. moha_10
    Best Response
    You've already chosen the best response.
    Medals 0

    15*ln(3x-11)=ln 225

    • one year ago
  15. moha_10
    Best Response
    You've already chosen the best response.
    Medals 0

    by multi 3 into 5 to get 15 and the exponent it's added

    • one year ago
  16. pratu043
    Best Response
    You've already chosen the best response.
    Medals 1

    But how can you just multiply the base and add the exponents?

    • one year ago
  17. waterineyes
    Best Response
    You've already chosen the best response.
    Medals 3

    Use the following formulas of Logs: \[\large Log(a \times b) = Log(a) + Log(b)\] \[\large Log(a)^b = b.Log(a)\]

    • one year ago
  18. moha_10
    Best Response
    You've already chosen the best response.
    Medals 0

    before we take the logarithem

    • one year ago
  19. moha_10
    Best Response
    You've already chosen the best response.
    Medals 0

    it's from exponent experepties

    • one year ago
  20. pratu043
    Best Response
    You've already chosen the best response.
    Medals 1

    Why did you delete that @dpaInc?

    • one year ago
  21. dpaInc
    Best Response
    You've already chosen the best response.
    Medals 0

    because i don't wanna take away from these guys awesome explanations....:)

    • one year ago
  22. waterineyes
    Best Response
    You've already chosen the best response.
    Medals 3

    See, take Log both the sides you will get: \[\large Log(5^{x-3}.3^{2x-8}) = Log(225)\] Now use the formulas I have written above..

    • one year ago
  23. waterineyes
    Best Response
    You've already chosen the best response.
    Medals 3

    Use the first formula only...

    • one year ago
  24. pratu043
    Best Response
    You've already chosen the best response.
    Medals 1

    \[\log(5^{x-3}) . \log(3^{2x-8}) = \log 225 \]

    • one year ago
  25. waterineyes
    Best Response
    You've already chosen the best response.
    Medals 3

    Now Check my first formula carefully...

    • one year ago
  26. moha_10
    Best Response
    You've already chosen the best response.
    Medals 0

    @pratu043 trust take my answer

    • one year ago
  27. moha_10
    Best Response
    You've already chosen the best response.
    Medals 0

    like what waterineyes did now

    • one year ago
  28. pratu043
    Best Response
    You've already chosen the best response.
    Medals 1

    That's what I've done here right @waterineyes?

    • one year ago
  29. waterineyes
    Best Response
    You've already chosen the best response.
    Medals 3

    I give you an example: \[\large Log(2 \times 3) = Log(2) + Log(3)\] Go by this procedure...

    • one year ago
  30. pratu043
    Best Response
    You've already chosen the best response.
    Medals 1

    I've already done that. So now we should use the second one?

    • one year ago
  31. waterineyes
    Best Response
    You've already chosen the best response.
    Medals 3

    You have done it wrongly my friend...

    • one year ago
  32. waterineyes
    Best Response
    You've already chosen the best response.
    Medals 3

    See check the formula.. After formula the result will be in sum form and your result is not in sum form.. Is there any + sign in your result???

    • one year ago
  33. pratu043
    Best Response
    You've already chosen the best response.
    Medals 1

    Oops. \[\log(5^{x-3}) + \log(3^{2x-8}) = \log225\]

    • one year ago
  34. waterineyes
    Best Response
    You've already chosen the best response.
    Medals 3

    Yes now you are right... Now 225 is square of what number???

    • one year ago
  35. pratu043
    Best Response
    You've already chosen the best response.
    Medals 1

    15

    • one year ago
  36. waterineyes
    Best Response
    You've already chosen the best response.
    Medals 3

    So can you write 225 as \(15^2\) on right hand side.?? If yes then do it..

    • one year ago
  37. pratu043
    Best Response
    You've already chosen the best response.
    Medals 1

    \[\log(5^{x-3}) + \log(3^{2x-8}) = \log15^{2}\]

    • one year ago
  38. waterineyes
    Best Response
    You've already chosen the best response.
    Medals 3

    Now use the power rule of Logarithms that is the Second Formula that I have given above.. Can you use that??

    • one year ago
  39. waterineyes
    Best Response
    You've already chosen the best response.
    Medals 3

    I give you an example of that too: \[\large Log(x)^4 = 4.Log(x)\]

    • one year ago
  40. pratu043
    Best Response
    You've already chosen the best response.
    Medals 1

    \[(x-3)\log5 + (2x-8)\log3 = 2\log15\]

    • one year ago
  41. waterineyes
    Best Response
    You've already chosen the best response.
    Medals 3

    Can you write 15 as 3*5??

    • one year ago
  42. pratu043
    Best Response
    You've already chosen the best response.
    Medals 1

    Yes. \[(x-3)\log5 + (2x-8)\log3 = 2\log(5 * 3)\]

    • one year ago
  43. waterineyes
    Best Response
    You've already chosen the best response.
    Medals 3

    Then use it and use the first formula again on right hand side...

    • one year ago
  44. pratu043
    Best Response
    You've already chosen the best response.
    Medals 1

    \[(x-3)\log5 + (2x-8)\log3 = 2\log5 + 2\log3\]

    • one year ago
  45. waterineyes
    Best Response
    You've already chosen the best response.
    Medals 3

    Now what you have to do is to compare the coefficients of \(Log3\) and \(Log5\) both the sides can you do that??

    • one year ago
  46. waterineyes
    Best Response
    You've already chosen the best response.
    Medals 3

    Tell me the coefficient of Log3 on Left hand side and right hand side...

    • one year ago
  47. pratu043
    Best Response
    You've already chosen the best response.
    Medals 1

    On LHS its 2x - 8 and on RHS its 2.

    • one year ago
  48. waterineyes
    Best Response
    You've already chosen the best response.
    Medals 3

    Just equate them and find x from it..

    • one year ago
  49. waterineyes
    Best Response
    You've already chosen the best response.
    Medals 3

    Similarly equate the coefficients of log5 and then also find x you will get the same x in both the case...

    • one year ago
  50. waterineyes
    Best Response
    You've already chosen the best response.
    Medals 3

    No no...

    • one year ago
  51. pratu043
    Best Response
    You've already chosen the best response.
    Medals 1

    \[(2x-8)\log3 = 2\log3\]

    • one year ago
  52. waterineyes
    Best Response
    You've already chosen the best response.
    Medals 3

    I said to equate the coefficients buddy.. Coefficients are 2x - 8 and 2.. you should equate this only...

    • one year ago
  53. pratu043
    Best Response
    You've already chosen the best response.
    Medals 1

    So you should just do 2x-8 = 2?

    • one year ago
  54. pratu043
    Best Response
    You've already chosen the best response.
    Medals 1

    x = 5

    • one year ago
  55. waterineyes
    Best Response
    You've already chosen the best response.
    Medals 3

    See, if : \[\large xlog3 = ylog3\] implies x = y. Getting??

    • one year ago
  56. pratu043
    Best Response
    You've already chosen the best response.
    Medals 1

    Yes!!

    • one year ago
  57. waterineyes
    Best Response
    You've already chosen the best response.
    Medals 3

    Yes you have found x = 5 that is absolutely right...

    • one year ago
  58. pratu043
    Best Response
    You've already chosen the best response.
    Medals 1

    Thanks a lot!!

    • one year ago
  59. waterineyes
    Best Response
    You've already chosen the best response.
    Medals 3

    Now equate the coefficients of log5..

    • one year ago
  60. pratu043
    Best Response
    You've already chosen the best response.
    Medals 1

    x - 3 = 2 x = 2 + 3 = 5

    • one year ago
  61. waterineyes
    Best Response
    You've already chosen the best response.
    Medals 3

    Yes got the same value of x so you are right.. If anyhow x values are coming different then either question is wrong or your solution is wrong.. Getting??

    • one year ago
    • Attachments:

See more questions >>>

Your question is ready. Sign up for free to start getting answers.

spraguer (Moderator)
5 → View Detailed Profile

is replying to Can someone tell me what button the professor is hitting...

23

  • Teamwork 19 Teammate
  • Problem Solving 19 Hero
  • You have blocked this person.
  • ✔ You're a fan Checking fan status...

Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.

This is the testimonial you wrote.
You haven't written a testimonial for Owlfred.