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Is 3x^2 - 2 > 0?

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fattty
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Is 3x^2 - 2 > 0? [#permalink] New post  13 Jan 2016, 23:35
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Is 3x^2 - 2 > 0?

(1) x < 4
(2) x > -3
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chetan2u
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Re: Is 3x^2 - 2 > 0? [#permalink] New post  14 Jan 2016, 00:16
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fattty wrote:
Is 3x^2 - 2 > 0?

(1) x < 4
(2) x > -3



Hi,
as usual , lets see the inequality and get some info out of it..
\(3x^2 - 2 > 0\)..
or \(x^2>\frac{2}{3}\)..
Now this to be true, x can not lie between \(\sqrt{\frac{2}{3}}\) and \(-\sqrt{\frac{2}{3}}\)

Lets see the statements now..
(1) x < 4
this range includes both x in between \(\sqrt{\frac{2}{3}}\) and \(-\sqrt{\frac{2}{3}}\) and x outside it... insuff

(2) x > -3
again this range includes both x in between \(\sqrt{\frac{2}{3}}\) and \(-\sqrt{\frac{2}{3}}\) and x outside it... insuff

combined.. the above point still remains.. insuff

E
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Re: Is 3x^2 - 2 > 0? [#permalink] New post  17 Jan 2016, 04:10
chetan2u wrote:
fattty wrote:
Is 3x^2 - 2 > 0?

(1) x < 4
(2) x > -3



Hi,
as usual , lets see the inequality and get some info out of it..
\(3x^2 - 2 > 0\)..
or \(x^2>\frac{2}{3}\)..
Now this to be true, x can not lie between \(\sqrt{\frac{2}{3}}\) and \(-\sqrt{\frac{2}{3}}\)

Lets see the statements now..
(1) x < 4
this range includes both x in between \(\sqrt{\frac{2}{3}}\) and \(-\sqrt{\frac{2}{3}}\) and x outside it... insuff

(2) x > -3
again this range includes both x in between \(\sqrt{\frac{2}{3}}\) and \(-\sqrt{\frac{2}{3}}\) and x outside it... insuff

combined.. the above point still remains.. insuff

E


hi! I've just put 2 conditions -

Statement 1 - x < 4

x could = -1 and answer would be yes
or
x = 0 and answer is no

These numbers work for statement 2 as well, thus E.

Is that logic right?
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chetan2u
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Joined: 02 Aug 2009
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Posts: 11157
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Re: Is 3x^2 - 2 > 0? [#permalink] New post  17 Jan 2016, 04:15
Expert Reply
lpetroski wrote:
chetan2u wrote:
fattty wrote:
Is 3x^2 - 2 > 0?

(1) x < 4
(2) x > -3



Hi,
as usual , lets see the inequality and get some info out of it..
\(3x^2 - 2 > 0\)..
or \(x^2>\frac{2}{3}\)..
Now this to be true, x can not lie between \(\sqrt{\frac{2}{3}}\) and \(-\sqrt{\frac{2}{3}}\)

Lets see the statements now..
(1) x < 4
this range includes both x in between \(\sqrt{\frac{2}{3}}\) and \(-\sqrt{\frac{2}{3}}\) and x outside it... insuff

(2) x > -3
again this range includes both x in between \(\sqrt{\frac{2}{3}}\) and \(-\sqrt{\frac{2}{3}}\) and x outside it... insuff

combined.. the above point still remains.. insuff

E


hi! I've just put 2 conditions -

Statement 1 - x < 4

x could = -1 and answer would be yes
or
x = 0 and answer is no

These numbers work for statement 2 as well, thus E.


Is that logic right?



Hi,
you are correct..
if you pick up two numbers in the range , each giving different answers yes and no....
the outcome will be that the statement is not sufficient..
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Re: Is 3x^2 - 2 > 0? [#permalink] New post  08 Oct 2022, 10:02
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