Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: A lil algebra help

  1. Sep 14, 2005 #1

    DB

    User Avatar

    to solve for d_2:
    [tex]\frac{336}{81}=\frac{175}{100}*\frac{1}{[\frac{d_2}{0.1}]^3}[/tex]
    [tex]\sim 2.4=\frac{1}{[\frac{d_2}{0.1}]^3}[/tex]

    then i dont know wat to do :mad: i know its simple algebra, i just dont see it,.
     
  2. jcsd
  3. Sep 14, 2005 #2

    Doc Al

    User Avatar

    Staff: Mentor

    If [tex]a = \frac{1}{b^3}[/tex]
    Then [tex]b^3 = \frac{1}{a}[/tex]

    Use this idea and keep going.
     
  4. Sep 14, 2005 #3

    DB

    User Avatar

    thnx 4 all the help doc,
    i get
    [tex]d_2=0.041^{\frac{1}{3}}[/tex]
     
  5. Sep 14, 2005 #4

    Doc Al

    User Avatar

    Staff: Mentor

    That doesn't seem right. Consider the following:
    [tex][\frac{d_2}{0.1}]^3 = \frac{d_2^3}{0.001}[/tex]
     
  6. Sep 14, 2005 #5

    DB

    User Avatar

    o i see wat i did, so [tex]d_2=[4.1*10^{-4}]^\frac{1}{3}[/tex]?
     
  7. Sep 14, 2005 #6

    Doc Al

    User Avatar

    Staff: Mentor

    Much better.
     
  8. Sep 14, 2005 #7

    Ouabache

    User Avatar
    Science Advisor
    Homework Helper

    Even better if you don't convert your constants to a decimal so soon.
    Keep them as fractions and you should find you can easily take their cube root later. :wink:
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook