It is currently 21 Oct 2017, 03:47

### 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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# Number properties I question #2

Author Message
Manager
Joined: 08 Nov 2009
Posts: 59

Kudos [?]: 9 [0], given: 3

Location: United States
Concentration: Strategy, Sustainability
WE: Supply Chain Management (Hospitality and Tourism)
Number properties I question #2 [#permalink]

### Show Tags

27 Nov 2009, 14:43
I tried looking for an explanation for this before posting but hand no luck. If some one could point me to a thread that would be great!

Is $$A$$ positive?

1. $$x^2 - 2x + A$$ is positive for all $$x$$
2. $$Ax^2 + 1$$ is positive for all $$x$$

My question is is on statement 1, if x=-1 wouldnt it be possible for A to be negative? -1^2 + -2*(-1) + A = 1+2+A =3+A. Therfore A could be -2 and the statement would still be positive.

What am i missing here?

Thanks,

Kudos [?]: 9 [0], given: 3

Joined: 20 Aug 2009
Posts: 305

Kudos [?]: 161 [1], given: 69

Location: Tbilisi, Georgia
Schools: Stanford (in), Tuck (WL), Wharton (ding), Cornell (in)
Re: Number properties I question #2 [#permalink]

### Show Tags

28 Nov 2009, 02:45
1
KUDOS
1. $$x^2 - 2x + A$$ is positive for all x

When x=0, $$x^2 - 2x + A=A$$. According to Statement1 it should be positive, so$$A>0$$, SUFF

2.$$Ax^2 + 1$$ is positive for all x

$$Ax^2 + 1>0$$
$$Ax^2>-1$$

Here $$x^2$$ is always positive, but A could be both positive OR negative. Consider x=1/3, A=-1; Ax^2=-1/9>-1

INSUFF

Kudos [?]: 161 [1], given: 69

Manager
Joined: 08 Nov 2009
Posts: 59

Kudos [?]: 9 [0], given: 3

Location: United States
Concentration: Strategy, Sustainability
WE: Supply Chain Management (Hospitality and Tourism)
Re: Number properties I question #2 [#permalink]

### Show Tags

28 Nov 2009, 07:53
Thanks for the clarification.

That helped me realize how i was thinking of A as a variable and not a constant.

Thanks,

Kudos [?]: 9 [0], given: 3

Re: Number properties I question #2   [#permalink] 28 Nov 2009, 07:53
Display posts from previous: Sort by

# Number properties I question #2

Moderator: Bunuel

 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®.