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xy plane

This topic has 2 member replies
beater Master | Next Rank: 500 Posts Default Avatar
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xy plane

Post Thu Jan 01, 2009 1:05 pm
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    In the xy-plane, if line k has negative slope and passes through the point (-5,r), is the x intercept of line k positive?

    1. the slope of line k is -5
    2. r > 0

    Please support your answers with explanations. Thanks!

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    logitech Legendary Member
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    Post Thu Jan 01, 2009 3:27 pm
    beater wrote:
    In the xy-plane, if line k has negative slope and passes through the point (-5,r), is the x intercept of line k positive?

    1. the slope of line k is -5
    2. r > 0

    Please support your answers with explanations. Thanks!
    y = mx+b , where m is the slope

    X intercept of the line is at (X,0) so :

    0 = mx+b

    x= -b/m

    so we will try to find out whether -b/m is positive or not.

    1) m=-5 no info given for b

    r = (-5)(-5)+b

    r = 25+b

    b=r-25 We dont know what r is so we can not decided whethjer -b/m is postive = 25-r/-5

    2) r > 0

    r = -5m+b



    -5m+b > 0

    b > 5m

    5m is a negative value since We know that slope is NEGATIVE

    so we can not decide whether b is positive or negative

    INSUF

    Statement 1 & 2

    r = 25+b

    25+b > 0

    b > -25

    It could be Postie or Negative

    So I would go with E

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    ronniecoleman Legendary Member
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    Post Thu Jan 01, 2009 11:03 pm
    In the xy-plane, if line k has negative slope and passes through the point (-5,r), is the x intercept of line k positive?

    1. the slope of line k is -5
    2. r > 0

    equation of a line

    Y = MX + C

    given that m = -ve

    r = -5m + c

    c = r+5m

    x intercept is - c/m


    now since m is negative , c has to be postive to make the intercept postive

    r+5m

    1) m = -5

    r -25

    no idea about r


    2) r > 0

    still no clue

    togther too we cannot find...

    IMO E

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