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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
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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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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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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