1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
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: Quick way to simplify (12(sqrt(2) + 17)

  1. Jan 29, 2009 #1
    1. The problem statement, all variables and given/known data

    This isn't really a problem at all. Have been working on some problems in Mary L Boas' textbook with some difficulty, but I have managed to solve the majority of the questions eventually. However, I've been stumped at how to arrive at the precise answers quoted in the book.

    For instance, one of the answers is [tex]\frac{1}{32} (51\sqrt{2} - ln (1 + \sqrt{2})[/tex]. But due to the method of arriving at the answer, my answer was [tex]\frac{1}{32}(51\sqrt{2}) - \frac{1}{128}(ln (17 + 2\sqrt{2})[/tex] which is equivalent (12 root 2 + 17 = (1 + rt 2)^4, after working backwards). But I'm wondering if there's actually a way to factorise or simplify my original (12 rt 2 + 17) quickly without working backwards.
  2. jcsd
  3. Jan 29, 2009 #2


    User Avatar
    Science Advisor
    Homework Helper

    Hi bigevil! :smile:

    (have a square-root: √ :wink:)

    This is a bit of a hindsight way too …

    you could have noticed that (17 + 12√2)(17 - 12√2) = 289 - 288 = 1,

    so any factor was going to have the same property …

    like 1 ± √2 and 3 ± 4√2 :smile:
  4. Jan 29, 2009 #3
    Thanks tim! That's pretty clever...
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook