In: Advanced Math
(c) [2] For which of the following functions are the level curves linear?
(I) f(x, y) = tan(x + y)
(II) g(x, y) = e^y/x (e to the power of y over x)
(III) h(x, y) = ln(xy)
(A) none (B) I only (E) I and II (F) I and III
(C) II only (G) II and III
(D) III only (H) all three
A partial table of values for a function f(x,y) is given below. Which of the following are positive?
(I) fy(4, 1)
(II) fx(4, 1) (III) fxx(4, 1)
| 
 x=3  | 
 x=4  | 
 x=5  | 
 x=6  | 
|
| 
 y=0  | 
 2.3  | 
 2.2  | 
 2.0  | 
 1.7  | 
| 
 y=1  | 
 2.4  | 
 2.5  | 
 2.7  | 
 3.0  | 
| 
 y=2  | 
 2.5  | 
 2.7  | 
 2.9  | 
 3.2  | 
| 
 y=3  | 
 2.6  | 
 3.0  | 
 3.0  | 
 3.3  | 
3.
Thus
it is not a linear equation . so only option I is a linear eqn
Option B only I is correct.
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