Results 1 to 4 of 4

Math Help - Solving inequalities??

  1. #1
    Newbie pinky&thebrain's Avatar
    Joined
    Mar 2005
    Posts
    19

    Solving inequalities??

    This is another one I am having trouble with:

    -2x - 5 >= -7

    Do I have to change the direction of the inequality?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Site Founder MathGuru's Avatar
    Joined
    Mar 2005
    From
    San Diego
    Posts
    478
    Awards
    1

    To Solve an Inequality

    -2x - 5 >= -7

    The goal here is to get the variable x on one side of the inequality and all the rest on the other side.

    The first thing we can do is add 5 to both sides which gives us

    -2x >= -2

    The next thing we can do is divide both sides by 2 which give us

    -x >= -1

    Now here is the tricky part, we multiply by -1, and yes we must change the direction of the inequality. The answer is:

    x <= 1

    Consider the following inequality

    -3 <= 4 This equation is true but if you multiply by -1

    3 <= -4 This equation is not true

    3 >= -4 This one is correct

    When multiplying by -1 we must change the direction of the inequality for the equation to remain true.

    Math Guru
    Last edited by MathGuru; March 29th 2005 at 09:30 AM.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member mattballer082's Avatar
    Joined
    Mar 2005
    From
    Los angeles
    Posts
    27
    yes. the rule is always when dividing (or multiplying????) by a negative, the inequality must be switched right?
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Site Founder MathGuru's Avatar
    Joined
    Mar 2005
    From
    San Diego
    Posts
    478
    Awards
    1

    Multiplying or Dividing

    Yes that is correct. The inequality is switched when multplying or dividing by a negative number.

    Math Guru
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Solving Inequalities
    Posted in the Algebra Forum
    Replies: 2
    Last Post: October 8th 2009, 04:57 AM
  2. Solving Inequalities
    Posted in the Algebra Forum
    Replies: 1
    Last Post: February 11th 2008, 01:01 PM
  3. Solving Inequalities
    Posted in the Algebra Forum
    Replies: 1
    Last Post: February 2nd 2008, 02:00 AM
  4. Solving Inequalities
    Posted in the Algebra Forum
    Replies: 2
    Last Post: January 13th 2008, 08:21 PM
  5. Solving inequalities
    Posted in the Algebra Forum
    Replies: 4
    Last Post: February 17th 2007, 04:12 PM

Search Tags


/mathhelpforum @mathhelpforum