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Homework Help: Radicals equations-negative square root and two radicals

  1. Dec 5, 2012 #1
    Is the answer to sqrt -81y^3 : y sqrt-81y? or is there no real solutions?

    Also for this radical equation:
    sqrt 2n-5 - sqrt 3n+4=2
    I worked it out and cant seem to get an answer. Is there no real solutions?
  2. jcsd
  3. Dec 5, 2012 #2


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    2017 Award

    Staff: Mentor

    if y<0, then ##\sqrt{-81y^3}=|y|\sqrt{-81y}##, otherwise the square root is not defined in the real numbers.

    Your equation has no real solutions. You can check this with WolframAlpha, for example.
  4. Dec 5, 2012 #3
    thank you so much, that WolframAlpha thing is very useful!
  5. Dec 5, 2012 #4


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    Homework Helper

    That [itex] \sqrt{-81 y} [/itex] can be further simplified by noting that 92 = 81 and -y = |y| , for y smaller or equal to 0.
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