1. Not finding help here? Sign up for a free 30min 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!

Solving Radical Equations

Tags:
  1. Jan 9, 2017 #1
    1. The problem statement, all variables and given/known data
    (Square root)-12 -3x - 3 = 0
    Everything underline is supposed to be under the square root sign.

    2. Relevant equations


    3. The attempt at a solution
    (Square root3x +12)2 = (3)2
    3x + 12 = 9
    -12 -12
    3x = -3
    x = -1
    Solution in this learning guide says the answer is -7. So I'm just wondering where I went wrong.
    If anyone knows how to make a square root symbol, please let me know.
     
  2. jcsd
  3. Jan 9, 2017 #2

    Mark44

    Staff: Mentor

    No. Your equation is ##\sqrt{-12 - 3x} = 3##
    If you square the left side, you get -12 - 3x, not 12 + 3x.
    I get x = -7 as well.
     
  4. Jan 9, 2017 #3

    Mark44

    Staff: Mentor

    BTW, I changed your thread title from "Solving Ration Equations" to "Solving Radical Equations."
    Yours is not a rational equation, which would involve a quotient of two polynomials.
     
  5. Jan 9, 2017 #4
  6. Jan 9, 2017 #5
    I thought you couldn't square a negative number?
     
  7. Jan 9, 2017 #6
    there is no square root of a negative number, no even nth root of any negative number
    there are odd nth roots of negative numbers...

    eg square root of -1 is not a real number, but cube root of -1 is -1.
     
  8. Jan 9, 2017 #7
    So as long as there are undefined units then you can square it?
     
  9. Jan 9, 2017 #8
    Sorry If I am confusing, all variables like X Y evaluate to a number, the squaring of a negative number is positive.

    The square root or even nth root of a negative number is not defined in terms of a real number.

    You can square a negative number to get a positive.

    -1 *-1 = 1.

    sQAURE ROOT =/= squaring.
     
  10. Jan 9, 2017 #9
    Ohhh, duh. Sorry! I understand now.
     
  11. Jan 9, 2017 #10

    Ray Vickson

    User Avatar
    Science Advisor
    Homework Helper

    Of course you can square a negative number. That is why an equation like ##x^2 = 9## has two solutions: ##x = 3## and ##x = -3##. Both give 9 when you square them.

    Perhaps you meant that you cannot take the square root of a negative number (in the real number system). But in the complex number field we can very nicely take the square root of a negative number, to get a so-called imaginary number. (It might surprise you to know that such things are used all the time by physicists and electrical engineers, among others.)
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Solving Radical Equations
  1. Solve radical equation (Replies: 6)

  2. Radical equation (Replies: 6)

Loading...