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by krishna kumar » Tue Jul 20, 2010 2:05 am
Hi ,

Could not get this...


Is A positive?

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

OA A


I am getting E .

my 2 cents worth.

Krishna Kumar
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Source: — Data Sufficiency |
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by sumanr84 » Tue Jul 20, 2010 2:27 am
krishna kumar wrote:Hi ,

Could not get this...


Is A positive?

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

OA A


I am getting E .

my 2 cents worth.

Krishna Kumar
St1 : Put x=0 or x=2
we get A > 0 Sufficient
St 2 : put x = 1
we get A+1 > 0 or A > -1 Not sufficient

IMO : A
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by Vipulvp » Tue Jul 20, 2010 3:33 am
krishna kumar wrote:Hi ,

Could not get this...


Is A positive?

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

OA A


I am getting E .

my 2 cents worth.

Krishna Kumar
First stmt indicates that the expression x^2 - 2x + A never intersects X-axis. i.e..the equation x^2 - 2x + A = 0 doesn't have real roots. This is possible if 4 - 4A >= 0 or A > = 1. So A is positive. sufficient.

Statement 2 can be false for x = 0.5 and A = -0.5. In this case the expression is still positive for a negative A. not sufficient. Hope this helps.
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