GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 22 Oct 2018, 00:50

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# In the xy-coordinate plane, the graph of y=x^2-kx-6, where

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:

### Hide Tags

Intern
Joined: 22 Feb 2014
Posts: 5
In the xy-coordinate plane, the graph of y=x^2-kx-6, where  [#permalink]

### Show Tags

Updated on: 29 Oct 2017, 20:52
2
11
00:00

Difficulty:

5% (low)

Question Stats:

85% (01:38) correct 15% (01:57) wrong based on 286 sessions

### HideShow timer Statistics

In the xy-coordinate plane, the graph of $$y=x^2-kx-6$$, where k is a constant, crosses the x-axis at two points. What is the value of k?

(1) For each of the two points where the graph crosses the x-axis, the x-coordinate is an integer.
(2) The graph crosses the x-axis at (1,0).

Originally posted by tr1 on 26 Feb 2014, 07:44.
Last edited by Bunuel on 29 Oct 2017, 20:52, edited 2 times in total.
Edited the question.
Math Expert
Joined: 02 Sep 2009
Posts: 50036
Re: In the xy-coordinate plane, the graph of y=x^2-kx-6, where  [#permalink]

### Show Tags

26 Feb 2014, 08:06
4
4
tr1 wrote:
Hey everybody,

this forum has helped me immensely in analyzing my wrong answers on the GMATprep tests. I have not found an explained answer to this question yet, so here we go:

In the xy-coordinate plane, the graph of $$y=x^2-kx-6$$, where k is a constant, crosses the x-axis at two points. What is the value of k?

(1) For each of the two points where the graph crosses the x-axis, the x-coordinate is an integer.
(2) The graph crosses the x-axis at (1,0).

Thanks,
Tim

In the xy-coordinate plane, the graph of $$y=x^2-kx-6$$, where k is a constant, crosses the x-axis at two points. What is the value of k?

(1) For each of the two points where the graph crosses the x-axis, the x-coordinate is an integer.

If $$y=(x+2)(x-3)=x^2-x-6$$, so if the x-intercepts, are -2 and 3, then k=1;
If $$y=(x-2)(x+3)=x^2+x-6$$, so if the x-intercepts are 2 and -3, then k=-1.

Not sufficient.

You could notice that $$y=x^2-kx-6$$ can be factored in many ways so that x-intercepts are integers:
$$y=(x+2)(x-3)$$,
$$y=(x-2)(x+3)$$,
$$y=(x+6)(x-1)$$,
$$y=(x-6)(x+1)$$,
...

(2) The graph crosses the x-axis at (1,0) --> substitute x=1 and y=0, into the equation: $$0=1^2-k-6$$ --> k=-5. Sufficient.

Hope this helps.
_________________
##### General Discussion
Intern
Joined: 22 Feb 2014
Posts: 5
Re: In the xy-coordinate plane, the graph of y=x^2-kx-6, where  [#permalink]

### Show Tags

26 Feb 2014, 08:17
This clears it up, thanks a lot!
Non-Human User
Joined: 09 Sep 2013
Posts: 8515
Re: In the xy-coordinate plane, the graph of y=x^2-kx-6, where  [#permalink]

### Show Tags

29 Oct 2017, 15:05
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
Re: In the xy-coordinate plane, the graph of y=x^2-kx-6, where &nbs [#permalink] 29 Oct 2017, 15:05
Display posts from previous: Sort by

# In the xy-coordinate plane, the graph of y=x^2-kx-6, where

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.