X^3 . y^2. z >0 => this product is +ve. As y^2 will always +ve, for making full term +ve there are 2 ways..
1) X^3 and z both are +ve => X>0 abd z>0
2) both are -ve => X<0 and z<0.

now
(1) XZ<0 = either X or y is -ve. irrispective of value of y this statment nagate the statement in question. SUFF.
(2)alone y>0 is not helping us as this is anyways not affecting the sigh of over all term as y^2 will be +ve for any value of y. NOT SUFF

Ans : A

Cartera,
Please use parenetheses if possible.

Its very easy to read the question as x^3y^2z

as x raised to power 3y again raised to power 2z. The question then becomes a little interesting.


Is the question x^3 * y^2 * z like Welcome has solved?

Regards,
CR

x^3y^2z>0?
(1)xz<0
(2)y>0

with the 1st statement, what if y is 0? (x^3)(0^2)z=0--then it is not >0, then statement 1 is not valid...

This can be written as
(x^2)(y^2)(xz)

The (x^2)(y^2) will be positive in all cases except if x or y is 0.

If both 1 and 2 are considered as correct, this means, neither x nor y is 0.

I will go with - Both togther are sufficient.