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 Your Progress

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

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

Re: Which of the following is a possible equation for the above graph? [#permalink]

Show Tags

10 Aug 2009, 22:00

8

This post received KUDOS

1

This post was BOOKMARKED

The graph is a plot of y=f(x) ,which we have to find. Look at the graph closely. The graph cuts at (0,0)

So when x=0, y =0 . This eliminates option B and E. When you substitute 0 in option B, y= x^3 - 1, if x=0 -> y=0^3 -1 =-1. The corresponding co-ordinate is 0,-1 which is not the case with the graph

When you substitute 0 in option E , y= x^3+3x^2-x+2 , if x=0 y= 2. Again, the corresponding co-ordinate is 0,2 which is not the case.

Now we are left with options A,C and D.

In A, y =x^3. If x>0, y should be greater than 0. But this is not the case in the given graph. The graph has points in 4th quadrant which is (x,-y). So option A can be ruled out.

Now consider C , y=3x^3 + 2x. Again if x>0 , y should be greater than 0. Ex. if x=1 , y= 5. if x=1/10 , y = 0.003+ 0.2 = 0.203. But this is not the case in the given graph. The graph has points in 4th quadrant which is (x,-y). So option C can be ruled out.

Now consider D, y= 3x^3 -2x , In this case , for x>0 , y can be gretaer than 0 or less than 0. For ex, if x=1/10, y= 0.003-.02= -0.017. If x=1, y =1. For x=2, y=22. So for x> 0, Y can be less than or greater than 0, spanning I and IV quadrant. Therefore option D is correct.

Re: Which of the following is a possible equation for the above graph? [#permalink]

Show Tags

11 Aug 2009, 02:14

D it is I don't think we can use the slope formula here... its a simple case of solving for X or Y and seeing the corresponding points on the graph.

What the source?
_________________

If you have made mistakes, there is always another chance for you. You may have a fresh start any moment you choose, for this thing we call "failure" is not the falling down, but the staying down.

Re: Which of the following is a possible equation for the above graph? [#permalink]

Show Tags

11 Aug 2009, 03:14

Just use elimination, or substitution, when u sub in (0,0), u eliminate two choices, and when u sub in a small number, u elminate A and C. then u are left with D

Re: Which of the following is a possible equation for the above graph? [#permalink]

Show Tags

16 Nov 2015, 07:07

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: Which of the following is a possible equation for the above graph? [#permalink]

Show Tags

23 Nov 2015, 10:28

Pretty sure calculus is not in the scope of the GMAT, so I apologize if this is a waste of time, but differentiation comes in handy here. There should be 2 points where the first derivative equals zero, i.e. a quadratic equation with 2 distinct roots for the local minima and maxima. This rules out A,B,and C. To decide between D and E, we apply second order conditions;we know that there is one inflection point at the origin, therefore the second derivative must = 0 where x = 0. For D, we have dy/dx = 9x^2 - 2; d2y/dx2 = 18x = 0, gives x=0, as required. Choose D. For E, we have dy/dx = 3x^2+6x-1. d2y/dx2 = 6x+6 =0. x is not 0. The answer is D

Re: Which of the following is a possible equation for the above graph? [#permalink]

Show Tags

11 Sep 2017, 03:42

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.
_________________

The graph shows that at x=0, y=0. Putting the value of x=0 in the above 5 equation will give that only A, C and D are left. B and E are out. Now we will have to calculate the slope. So using the concept of differentiation the formula for slope are as follows. A -> 3\(x^2\) C -> 9\(x^2\) + 2 D -> 9\(x^2\) - 2

From the graph we also know that the slope at x=0 is -ve Putting the value of x=0 in the above 3 equations, we get

A -> 3\(0^2\) --> 0 C -> 9\(0^2\) + 2 --> 2 D -> 9\(0^2\) - 2 --> -2

Only D satisfied the required condition,

Hence answer is D
_________________

------------------------------------------------------------------------------- Kudos are the only way to tell whether my post is useful.