x(y^2)(z^3)<0?

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x(y^2)(z^3)<0?

by ska7945 » Fri Sep 05, 2008 7:02 am
if xyz>0. is x(y^2)(z^3)<0?



1.y<0

2.x>0

oa a
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by mayur00 » Fri Sep 05, 2008 8:26 am
Given xyz>0, possible signs for x, y, z will be as follows:

x y z
+ + +
+ - -
- + -
- - +

1. y<0

Looking at the above list if y<0 then either x is positive and z is negative or x is negative and z is positive.

In either case x * (y^2) * (z^3) <0

So. 1 is sufficient.


2. x>0

Again from the table above is x>0, then either both y and z are positive or negative.

When both y and z are positive x * (y^2) * (z^3)>0

When both y and z are negative x * (y^2) * (z^3)<0

Therefore insufficient.


Hence answer is A