Let $f ( x , y , z ) = \frac { x } { y } + \frac { y } { z } + \frac { z } { x }$

Short Answer

Let $f ( x , y , z ) = \frac { x } { y } + \frac { y } { z } + \frac { z } { x }$ . Find the rate of change of $f$ at $P ( 1 , - 1,1 )$ in the direction from $P$ toward $( 2,1,0 )$ .