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

Simplifying radical equations

  1. Apr 18, 2004 #1
    sqrt(11+sqrt72)) + sqrt(11-sqrt(72))

    better picture here

    I don't know where to begin for this one, but apparently my calculator says the answer is 6 :redface:
  2. jcsd
  3. Apr 18, 2004 #2

    matt grime

    User Avatar
    Science Advisor
    Homework Helper

    let x be the surd, square x, what do you get?
  4. Apr 18, 2004 #3
    let x be the "surd"?
  5. Apr 18, 2004 #4
    ok, set sqrt(11+sqrt72)) + sqrt(11-sqrt(72)) = x
    (by the way, sqrt(72) = 6*sqrt(2), which i'll just call 6r2 for simplicity)
    square both sides, we get
    (sqrt(11+sqrt72)) + sqrt(11-sqrt(72)))^2 = x^2
    simplify and you get
    x=6 (well, plus or minus, but we know it must be positive since the addition of two non-complex roots must be >= 0)
  6. Apr 18, 2004 #5

    matt grime

    User Avatar
    Science Advisor
    Homework Helper

    Yes, surd: an expression involving radicals. I just didn't want to have to type it out. Just square the expression, simplify and take the square root, et voila, we have 6, with the appropriate choice of sign.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Simplifying radical equations
  1. Simplify equation (Replies: 3)