If x^5y^4z^2 <0 , which of the following must be true?
I. xy <0
II. yz <0
III. xz <0 Choose the correct option:	A) I	B) II	C) III	D) I and II	E) None
Ans:- x^5y^4z^2 &lt;0   x must be negative. x&lt;0 ; y and z can be either negative or positive as even powers is always positive.   I. xy &lt;0 :- x&lt;0 but y can be - or + hence xy &lt; 0 when y&gt;0 or xy &gt;0 when y &lt;0. So not always true.   II. yz &lt;0 :- As both y and z can be + or - ; yz &lt; 0 or yz &gt;0 are possible   II. xz &lt;0 :- x&lt;0 but z can be - or + hence xz &lt; 0 when z&gt;0 or xz &gt;0 when z &lt;0. So not always true.   Ans :- None
<result>E</result>
If x^5y^4z^2 <0 , which of the following must be true?
I. xy <0
II. yz <0
III. xz <0