Results 1 to 2 of 2

Math Help - Please help with an ln problem

  1. #1
    Junior Member
    Joined
    Nov 2009
    Posts
    39

    Please help with an ln problem

    Can anyone help with this problem?

    ln(r^3s^7([7th root](r^7s^10)))

    is equal to A ln r +B ln s

    where A=______ and B=________

    This is what I have so far:
    3 ln r + 7 ln s + 7th root (r^7s^10)

    I thought it should be
    3 ln r + 7 ln s + 49/2 ln r + 70/2 ln s=
    55/2 ln r + 84/2 ln s

    but that is wrong. How do you do the 7th root?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,928
    Thanks
    757
    Quote Originally Posted by operaphantom2003 View Post
    Can anyone help with this problem?

    ln(r^3s^7([7th root](r^7s^10)))

    is equal to A ln r +B ln s

    where A=______ and B=________

    This is what I have so far:
    3 ln r + 7 ln s + 7th root (r^7s^10)

    I thought it should be
    3 ln r + 7 ln s + 49/2 ln r + 70/2 ln s=
    55/2 ln r + 84/2 ln s

    but that is wrong. How do you do the 7th root?
    \ln(r^3 s^7 \sqrt[7]{r^7 s^{10}})

    \ln(r^3 s^7 \cdot r s^{\frac{10}{7}})

    \ln(r^4 s^{\frac{59}{7}})

    \ln(r^4) + \ln(s^{\frac{59}{7}})

    4\ln{r} + \frac{59}{7}\ln{s}
    Follow Math Help Forum on Facebook and Google+

Search Tags


/mathhelpforum @mathhelpforum