Does line y = mx + c intersect X axis? : GMAT Data Sufficiency (DS)
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# Does line y = mx + c intersect X axis?

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Does line y = mx + c intersect X axis? [#permalink]

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03 Feb 2011, 12:16
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Does line y = mx + c intersect X axis?

(1) m < 0
(2) c > 0
[Reveal] Spoiler: OA

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Re: Does line y = mx + c intersect X axis? [#permalink]

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03 Feb 2011, 19:43
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Statement 1 Alone:
It is given that the slope of the line is negative. Thus, at one point or other, it will intersect the x-axis.

The point at which it will intersect the x-axis is:

mx + c = 0 or x = -c/m

SUFFICIENT

Statement 2 Alone:
It is given that the y intercept is greater than 0. This means that the line intersects the y axis at a point y>0.
It is not necessary for the line to intersect the x-axis because the line can be parallel to the x-axis while having a positive y intercept

Ans: 'A'
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Does line y = mx + c intersect X axis? [#permalink]

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26 Sep 2013, 22:58
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Does line y = mx + c intersect X axis?

(1) m < 0
(2) c > 0
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Re: Does the line Y=MX+C intersect X axis? [#permalink]

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26 Sep 2013, 23:12
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KK23 wrote:
Does line Y=MX+C intersect X axis?

A)M<0

B)C>0

Statement 1 : M<0 means slope is negative,
so at some point the line will intersect x.

intersection point :
mx+c=0, so x= -c/m... (A is sufficient)

Statement 2: y intercept is greater than 0, so it will intersect y>0.

This line may be parallel to x-axis with positive y intercept.. so not sufficient.

Answer is A Hope it is correct. i guess i came across this problem earlier in Club forum
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Re: Does the line Y=MX+C intersect X axis? [#permalink]

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26 Sep 2013, 23:41
GNPTHBALAJI wrote:
KK23 wrote:
Does line Y=MX+C intersect X axis?

A)M<0

B)C>0

Statement 1 : M<0 means slope is negative,
so at some point the line will intersect x.

intersection point :
mx+c=0, so x= -c/m... (A is sufficient)

Statement 2: y intercept is greater than 0, so it will intersect y>0.

This line may be parallel to x-axis with positive y intercept.. so not sufficient.

Answer is A Hope it is correct. i guess i came across this problem earlier in Club forum

+1 Kudos....

Thanks a lot !!!

Any idea is if we have a quadratic equation f(x)=Ax^2+C=y will this intersect with x axis if we know that A<0 or C>0??
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Re: Does line y = mx + c intersect X axis? [#permalink]

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27 Sep 2013, 01:01
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Expert's post
KK23 wrote:
Does line y = mx + c intersect X axis?

(1) m < 0
(2) c > 0

Check here for theory: math-coordinate-geometry-87652.html

Hope it helps.
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Re: Does line y = mx + c intersect X axis? [#permalink]

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27 Sep 2013, 01:30
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The first statement (m<0) alone is sufficient to answer but not the second statement (c>0) alone.

The reason is that if m=0, then the line is parallel to Y-axis, hence won't intersect the X-axis. Since m<0, it is a line with decreasing slope, hence the line will intersect and cut the X-axis at a certain stage.

As for the statement 2 (c>0), it may or may not intersect the X-axis as the line may be parallel to X - axis and still have a positive c. Example : y = 5 is a straight line with c = 5 >0 and won't ever cut the X-axis.
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Re: Does line y = mx + c intersect X axis? [#permalink]

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09 Oct 2014, 00:27
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Re: Does line y = mx + c intersect X axis? [#permalink]

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06 Apr 2016, 08:21
Hello from the GMAT Club BumpBot!

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Re: Does line y = mx + c intersect X axis? [#permalink]

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19 Sep 2016, 04:01
mx + c = 0 or x = -c/m
.pls explain this part.pls
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Re: Does line y = mx + c intersect X axis? [#permalink]

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19 Sep 2016, 04:16
sanaexam wrote:
mx + c = 0 or x = -c/m
.pls explain this part.pls

mx + c = 0;

mx = -c;

x = -c/m.
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Re: Does line y = mx + c intersect X axis? [#permalink]

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19 Sep 2016, 04:26
y=mx+c.how did y become 0?
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Re: Does line y = mx + c intersect X axis? [#permalink]

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19 Sep 2016, 04:33
sanaexam wrote:
y=mx+c.how did y become 0?

x-intercept is the value of x for y = 0.

Check here for theory: math-coordinate-geometry-87652.html
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Re: Does line y = mx + c intersect X axis? [#permalink]

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19 Sep 2016, 04:42
ok.now understood:)
Re: Does line y = mx + c intersect X axis?   [#permalink] 19 Sep 2016, 04:42
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