 
Summary: 14.1 Functions of Several Variables
Definition: Let . A
2
D function of two variables is a rule that assigns
a unique real number ( , )f x y to each point ( , )x y D .
The set D is called domain of ( , )f x y .
Definition: Let . A3
D function of three variables is a rule that
assigns a unique real number ( , , )f x y z to each point ( , , )x y z D .
The set D is called domain of ( , , )f x y z .
Question 10/898: For 2 2 2
( , , ) ln(25 )f x y z x y z=   
(a) Find (2, 2,4)f  (b) Find domain and range of ( , , )f x y z
(c) Sketch domain of ( , , )f x y z .
Question 16/898: Find and sketch domain of the function
( , ) ln( )y xf x y y x= + .
Exercise: Find domain of
1
( , )
1
