Results 1 to 2 of 2

Math Help - how to put an expression under the square root?

  1. #1
    Newbie
    Joined
    Jun 2010
    Posts
    13

    how to put an expression under the square root?

    So, let's say that you have this expression:
    (x - a)

    and you need to get it under the square root sign. What is the right way to do it?

    I came up with two methods, hopefully at least one of them is right. I want to find out which is right and to read more on the topic in order to understand WHY it is right.

    First way:


    <br />
x - a = \sqrt{x^2 - a^2} = \sqrt{(x-a)(x+a)}<br /> <br />



    Second way:


    <br />
x - a = \sqrt{(x-a)^2} = \sqrt{x^2 - 2xa + a^2}<br /> <br />



    I can't find any videos on youtube or texts on the math sites, because I don't know which keywords to use in order to find it - any help would be appreciated.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by Aero763 View Post
    So, let's say that you have this expression:
    (x - a)

    and you need to get it under the square root sign. What is the right way to do it?

    I came up with two methods, hopefully at least one of them is right. I want to find out which is right and to read more on the topic in order to understand WHY it is right.

    First way:


    x - a = \sqrt{x^2 - a^2} = \sqrt{(x-a)(x+a)} Mr F says: This is totally wrong. What happens if x = 2 and a = 1, for example? You're meant to learn something from previous questions that you posted: http://www.mathhelpforum.com/math-he...equal-1-a.html

    Second way:

    x - a = \sqrt{(x-a)^2} = \sqrt{x^2 - 2xa + a^2} Mr F says: This is wrong too. \sqrt{(x - a)^2} = |x - a| not x - a.

    I can't find any videos on youtube or texts on the math sites, because I don't know which keywords to use in order to find it - any help would be appreciated.
    Perhaps you should post the real question (the one that has led to what you posted).
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Square root inside square root equation
    Posted in the Algebra Forum
    Replies: 3
    Last Post: October 10th 2011, 04:17 PM
  2. square root + cube root of a number
    Posted in the Algebra Forum
    Replies: 2
    Last Post: December 5th 2010, 10:35 AM
  3. Replies: 12
    Last Post: November 22nd 2008, 12:41 PM
  4. Simplifying Square Root w/in square root
    Posted in the Algebra Forum
    Replies: 5
    Last Post: September 7th 2006, 08:01 AM
  5. Replies: 2
    Last Post: April 29th 2006, 01:13 AM

Search Tags


/mathhelpforum @mathhelpforum