Results are out! Find what you need...fast. Get quick advice or join the chat
Hey! Sign in to get help with your study questionsNew here? Join for free to post

Quick C3 integration

Announcements Posted on
Applying to Uni? Let Universities come to you. Click here to get your perfect place 20-10-2014
    • Thread Starter
    • 0 followers
    Offline

    ReputationRep:
    Was hoping someone could help on this please, integrating with limits 1 to 9
    \large \pi \int \frac{36}{3x-2}

    I pulled out the 36 from the numerator , and made it:
    \large 36\pi \int \frac{1}{3x-2}

    \large 36\pi ln(3x-2)

    After subbing in the limits I get the answer wrong as the answer given involves 12 pi ?

    I got 36Pi ln25 , answer is 12Pi ln25 , I thought my method would usually work for these.
    • 1 follower
    Offline

    ReputationRep:
    When you're integrating lnf(x), what's the rule?
    • 0 followers
    Offline

    ReputationRep:
    The format has to be f'(x)/f(x). So you have to take out 12, as then you're left with 3 at the top (the bottom differentiates to 3). You should be fine from there on out.
    • 0 followers
    Offline

    ReputationRep:
    notice you need a third of it
    • Thread Starter
    • 0 followers
    Offline

    ReputationRep:
    (Original post by RajPopat94)
    When you're integrating lnf(x), what's the rule?
    If it's 1/something, then ln(something) right ? , but I took out the 36 as a constant so that shouldn't matter ?
    • 46 followers
    Offline

    ReputationRep:
    (Original post by Tulian)
    If it's 1/something, then ln(something) right ? , but I took out the 36 as a constant so that shouldn't matter ?
     \displaystyle \int \frac{c}{ax+b} \ dx = c \int \frac{1}{ax+b} \ dx = c \times \frac1{a} ln|ax+b| + C
    • Thread Starter
    • 0 followers
    Offline

    ReputationRep:
    I totally forgot about the 1/a part after taking the 36 out.

    Thanks everyone

Reply

Submit reply

Register

Thanks for posting! You just need to create an account in order to submit the post
  1. this can't be left blank
    that username has been taken, please choose another Forgotten your password?
  2. this can't be left blank
    this email is already registered. Forgotten your password?
  3. this can't be left blank

    6 characters or longer with both numbers and letters is safer

  4. this can't be left empty
    your full birthday is required
  1. By joining you agree to our Ts and Cs, privacy policy and site rules

  2. Slide to join now Processing…

Updated: June 9, 2012
New on TSR

Personal statement help

Use our clever tool to create a PS you're proud of.

Article updates
Reputation gems:
You get these gems as you gain rep from other members for making good contributions and giving helpful advice.