Results 1 to 3 of 3

Math Help - Inequality :\

  1. #1
    Junior Member
    Joined
    Dec 2008
    From
    London
    Posts
    45

    Inequality :\

    Stupid inequality i can't solve, we've been told to show a certain method when solving the question which i don't understand T_T

    Question
    \frac{3}{3x-2}>\frac{1}{x+4}

    The method we are meant to use is supposed to involved these if statements (4 of them)

    1. If (x+4)(3x-2) are +ve then ans is ....
    2. If (x+4)(3x-2) are -ve then ans is ....
    3. If (x+4) is +ve and (3x-2) is -ve then ans is ....
    4. If (3x-2) is +ve and (x+4) is -ve then ans is ....

    I think i can do the 1st if statement
    \frac{3}{3x-2}>\frac{1}{x+4}
    If both denominators +ve multiply both sides by (x+4)(3x-2) which results in.
    3(x+4)>3x-2
    3x+12>3x-2
    14>0

    Got no idea how to do 2.3.4 someone help meee

    1.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Master Of Puppets
    pickslides's Avatar
    Joined
    Sep 2008
    From
    Melbourne
    Posts
    5,236
    Thanks
    28
    Quote Originally Posted by Kevlar View Post

    1. If (x+4)(3x-2) are +ve then ans is ....
    The > will not change


    Quote Originally Posted by Kevlar View Post

    2. If (x+4)(3x-2) are -ve then ans is ....
    If both terms are negative then the product will be positive and
    the > will not change.

    If (x+4)(3x-2) is all negative then the > will change to <

    Quote Originally Posted by Kevlar View Post

    3. If (x+4) is +ve and (3x-2) is -ve then ans is ....
    The > will change to < as the product is negative


    Quote Originally Posted by Kevlar View Post

    4. If (3x-2) is +ve and (x+4) is -ve then ans is ....
    The > will change to < as the product is negative
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Dec 2008
    From
    London
    Posts
    45
    Ok ima try the 2nd and 3rd ones then

    2. If (x+4) and (3x-2) are -ve then

    \frac{3}{3x-2}>\frac{1}{x+4}
    is multiplied on both sides by -(3x-2).-(x+4)

    -3.-(x+4)>-1.-(3x-2)
    3x+13>3x-2
    14>0

    ???? :z graphs dont intersect if both are +ve or both are -ve? :z

    3. If (x+4) is +ve, (3x-2) is -ve.

    \frac{3}{3x-2}>\frac{1}{x+4}
    is multiplied on both sides by -(3x-2).(x+4)

    -3.(x+4)<-(3x-2)
    -3x-12<-3x+2
    -14<0

    i think ive gone wrong arghttt
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 2
    Last Post: January 11th 2011, 08:20 PM
  2. Replies: 3
    Last Post: December 12th 2010, 01:16 PM
  3. inequality
    Posted in the Trigonometry Forum
    Replies: 1
    Last Post: July 26th 2010, 04:34 AM
  4. inequality
    Posted in the Algebra Forum
    Replies: 4
    Last Post: July 24th 2010, 12:08 PM
  5. Inequality
    Posted in the Algebra Forum
    Replies: 0
    Last Post: October 8th 2009, 03:06 AM

Search Tags


/mathhelpforum @mathhelpforum