Which of the following functions does not intersect with y = 3x^2 + 2x : Problem Solving (PS)

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Which of the following functions does not intersect with y = 3x^2 + 2x

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Which of the following functions does not intersect with y = 3x^2 + 2x [#permalink]

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Updated on: 14 Sep 2014, 15:49

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42% (01:47) wrong

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Which of the following functions does not intersect with y = 3x^2 + 2x + 1

A. y = 3x^2 + 3x + 1
B. y = 2x^2 + 3x + 1
C. y = 3x^2 + 2x + 3
D. y = 4x^2 + 2x - 3
E. y = x^2 + 2x + 3

This question is not from the OG, but I am stuck on this question. Can anyone help me?

Spoiler: OA

Originally posted by jkim1118 on 14 Sep 2014, 11:26.
Last edited by Bunuel on 14 Sep 2014, 15:49, edited 1 time in total.

Renamed the topic, edited the question and added the OA.

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Which of the following functions does not intersect with y = 3x^2 + 2x [#permalink]

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14 Sep 2014, 15:56

jkim1118 wrote:

The graph of y = 3x^2 + 2x + 3 (option C) gives the same parabola as y = 3x^2 + 2x + 1, just shifted 2 units up. So, they won't intersect:

Attachment:

MSP2631fcd0ab556630ba400002aef01a3gd12cb24.gif [ 5.36 KiB | Viewed 3066 times ]

Answer: C.

Similar question to practice: the-line-represented-by-which-of-the-following-equation-does-137828.html
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Re: Which of the following functions does not intersect with y = 3x^2 + 2x [#permalink]

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04 Oct 2014, 03:34

jkim1118 wrote:

If you are familiar with graphs, this question gets solved within a minute as shown by Bunuel... but I am not that comfortable with graphs...
I solved it by equating the the equation given in the question stem to the equation given in the answer choices...
A. y = 3x^2 + 3x + 1 = 3x^2 + 2x + 1.. this gives x=0 thus these two sets of equations intersect at x=0 and y=1
B. y = 2x^2 + 3x + 1 = 3x^2 + 2x + 1... this gives x^2 -x = 0 which means either x=0 or x=1. Thus these two intersect at 2 points.
C. y = 3x^2 + 2x + 3 = 3x^2 + 2x + 1.. this does not give a solution... thus the answer is C
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Re: Which of the following functions does not intersect with y = 3x^2 + 2x [#permalink]

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29 Oct 2015, 01:00

Forget conventional ways of solving math questions. In PS, IVY approach is the easiest and quickest way to find the answer.

Which of the following functions does not intersect with y = 3x^2 + 2x + 1

A. y = 3x^2 + 3x + 1
B. y = 2x^2 + 3x + 1
C. y = 3x^2 + 2x + 3
D. y = 4x^2 + 2x - 3
E. y = x^2 + 2x + 3

Let’s find the actual intersecting point of given function and each choice.
A. 3x^2 + 2x + 1 = 3x^2 + 3x + 1 --> x=0
B. 3x^2 + 2x + 1 = 2x^2 + 3x + 1 --> x^2 – x =0 --> x=0 or 1
C. 3x^2 + 2x + 1 = 3x^2 + 2x + 3 --> 1=3(X) --> they don’t have any intersect.
D. 3x^2 + 2x + 1 = 4x^2 + 2x - 3 --> x^2 –4=0 --> x= 2 or -2
E. 3x^2 + 2x + 1 = x^2 + 2x + 3 --> 2x^2 –2 =0 --> x= 1 or –1.

So only choice (C) has no intersecting point. The answer is (C).
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Which of the following functions does not intersect with y = 3x^2 + 2x [#permalink]

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06 Nov 2015, 21:40

Given function is a parabola with y intercept = 1

A and B out because they have y intercept=1

coefficient a before x^2 should be the same not to intersect

Only C, because only difference from given is that y intercept=3. So, it is just higher

C

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Re: Which of the following functions does not intersect with y = 3x^2 + 2x [#permalink]

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01 Nov 2017, 01:12

Hello Moderators,

The Tag for this question says this is an OG question. However, the comment from the poster says that it is not an OG question. Can you please confirm if this is actually an OG question, please?

I took too much time to solve this question. If this is an OG question, I need to practice more and find better ways of approaching these type of question

Thanks in advance.
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Re: Which of the following functions does not intersect with y = 3x^2 + 2x [#permalink]

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01 Nov 2017, 01:23

susheelh wrote:

Thanks in advance.

Removed the OG tag.

Parabolas and other graphs are tested on the GMAT though. OG questions:
https://gmatclub.com/forum/for-what-val ... 11639.html
https://gmatclub.com/forum/the-figure-s ... 60785.html
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Re: Which of the following functions does not intersect with y = 3x^2 + 2x [#permalink]

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01 Nov 2017, 02:08

let's "plug-in" each answer one by one. Only choice (C) has no intersecting point => answer C

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Re: Which of the following functions does not intersect with y = 3x^2 + 2x [#permalink]

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11 Dec 2017, 11:35

In order for two functions to intersect, substituting a certain x-value will produce the same y value for the two functions. With choice C, we can see the y value will ALWAYS be two more if we have the same x value. So the two functions can never intersect.