Results 1 to 3 of 3

Math Help - |x| + |y| = 4

  1. #1
    Newbie
    Joined
    Jul 2010
    Posts
    24

    Exclamation |x| + |y| = 4

    sir what if the question is like this?

    |x|+|y|=4 ?
    Last edited by mr fantastic; June 27th 2011 at 04:44 AM.
    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

    Re: |x| + |y| = 4

    Quote Originally Posted by ejaykasai View Post
    sir what if the question is like this?

    |x|+|y|=4 ?
    The graph is here: plot |x| + |y| = 4 - Wolfram|Alpha

    Knowing the answer, and understanding what |x| and |y| mean, you should be able to figure out where the answer comes from.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor

    Joined
    Apr 2005
    Posts
    15,720
    Thanks
    1472

    Re: |x| + |y| = 4

    Quote Originally Posted by ejaykasai View Post
    sir what if the question is like this?

    |x|+|y|=4 ?
    That's not a question- it is an equation. What do you want to do with it?
    If, as mr fantastic suggests, you want to graph it then do what is standard for absolute value: look at positive and negative values.

    If both x and y are non-negative, |x|= x, |y|= y so the equation becomes x+ y= 4. If x= 0, y= 4 and if y= 0, x= 4. That is a straight line, in the first quadrant, with endpoints (0, 4) and (4, 0). If x is negative, but y is positive, |x|= -x, |y|= y so the equation becomes -x+ y= 4 or y= x+ 4. When x= 0, y= 4. When y= 0, x= -4. That is a straight line, in the second quadrant, with endpoints (0, 4), (-4, 0). If both x and y are negative, |x|= -x, |y|= -y so the equation becomes -x- y= 4. If x= 0, y= -4 and if y= 0, x= -4. That is a straight line, in the third quadrant, with endpoints (0, -4) and (-4, 0). Finally, if x> 0, y< 0, |x|= x, |y|= -y and the equation becomes x- y= 4 or y= x- 4. If x= 0, y= -4. If y= 0, x= 4. Thatis a straight line, in the fourth quadrant, with endpoints (0, -4), (4, 0).

    Putting those all together, the graph is a square with diagonals along the x and y axes with vertices (4, 0), (0, 4), (-4, 0), (0, -4).
    Follow Math Help Forum on Facebook and Google+

Search Tags


/mathhelpforum @mathhelpforum