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Is 2st > 0?

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Senior Manager
Status: Gathering chakra
Joined: 05 Feb 2018
Posts: 434

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26 Mar 2019, 16:50
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Difficulty:

15% (low)

Question Stats:

82% (01:34) correct 18% (01:49) wrong based on 39 sessions

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Is 2st > 0?

(1) (t + s)² + (t – s)² > 0

(2) (t + s)² < (t – s)²
Math Expert
Joined: 02 Aug 2009
Posts: 8004
Re: Is 2st > 0?  [#permalink]

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27 Mar 2019, 01:39
Is 2st > 0?
This means is st>0, or s and t have SAME sign?

(1) (t + s)² + (t – s)² > 0
Squares are always non negative. So this just tells us S=t=0 is not possible..
Insufficient

(2) (t + s)² < (t – s)²
$$t^2+s^2+2st<t^2+s^2-2st......4st<0...st<0$$
Thus ans is no, st is not greater than 0..
Sufficient

B
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Re: Is 2st > 0?   [#permalink] 27 Mar 2019, 01:39
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