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Is x(y + z) > 0? 1) xyz > 0 2) yz > 0

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Is x(y + z) > 0? 1) xyz > 0 2) yz > 0 [#permalink] New post 28 Jul 2004, 02:58
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Is x(y + z) > 0?

1) xyz > 0
2) yz > 0
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 [#permalink] New post 28 Jul 2004, 04:08
E...

1) xyz > 0
2) yz > 0

from 2) ----- (y+z) can be negative/positive...
from 1) xyz > 0 implies that x can be positive when (y+z) is positive...
x can be negative when (y+z) is negative..

hence there can be no conclusion on x(y+z) > 0
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 [#permalink] New post 28 Jul 2004, 13:52
why not C

You said

from 2) ----- (y+z) can be negative/positive...
from 1) xyz > 0 implies that x can be positive when (y+z) is positive...
x can be negative when (y+z) is negative..


Which means that when (y+z) is negative then x is negative hence x(y+z)has to be positive > 0

When (y+z) positive then x is positive hence x(y+z) is postive. In both the cases x(y+z) is positive.


Where am I going wrong. My GMAT is in next couple of days oh god!!!
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 [#permalink] New post 28 Jul 2004, 13:59
hey pakoo,

one mistake. x can't be negative when y and z are both negative, because then the whole thing would be negative. in fact, when we look at them together, x is always positive. But we don't know if yz is neg or pos, so we can't answer it.

Good luck on your test!
  [#permalink] 28 Jul 2004, 13:59
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