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

ska7945 · Posted: Fri Sep 05, 2008 7:02 am Post subject: x(y^2)(z^3)<0?

if xyz>0. is x(y^2)(z^3)<0?

1.y<0

2.x>0

oa a

mayur00 · Posted: Fri Sep 05, 2008 8:26 am Post subject:

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