21.
f()- n , - - D(f). f() . , , , , =
=a
.. , - ,
21)
, (0,0):
(0; ) (;0)
1. = =-1 -1
2. = =-1
23.
() f(), , , =f(
,
f(x,y)= , + (0,0)?
24.
(1,0) ()
25. () , 0.
=
:0
26. ( 25)
=y*2x=4
= =1
27. z=f(x,y) (, ), :
= ( ) ,
- (x,y) ( )
z=f(x,y) (), .
-: ,
= = + + =0
28. z=f(x,y) ,
dz= , dx=
z= d
z=f(x,y) (, ), :
= ( ) ,
- (x,y) ( )
: z= -?
29. ?
=(grad f(M), )
() ()
= * *cos
, 0
. ,
grad f(M)=()
=(grad f(M), )= * *cos -
cos , ..
31. D Rn Rn, (x1, x2, ., xn) (tx1, tx2, ., txn) t>0 f(x1, x2, ., xn) D λ, t>0 f (tx1, tx2, ., txn)=tλ f(x1, x2, ., xn).
, . 2 . =t2
32. 3:
F (x,y)=x2
F (tx, ty)=t2x2√(tx*ty)=t3 F (x,y)
33. f (tx1, tx2,tx3)=tλ f(x1, x2, x3). u= f(x,y,z)
34. z=f(x;y) D (0;0) D ( D), (), e - , , (0;0) :
|
|
f(x;y)>f(0;0) min
f(x;y)<f(0;0) max
, .. .
35. f(x,y)=x6y4 (0,0)
x=0 y=0 |
(0,0) =0 >=0 : ( >=0)
36. f(x,y)=xy4 (0,0)
x=0 y=0 |
(0,0) = 0 : ( )
37. f(x.y)=x2-y2 (o,o)
x=0 y=0 |
=-4 <0 :
38. ) Fx=2x Fy=2y
(1,1) , (1,1) ( ).
) x+y=2. Y=2-x
f= x2+(2-x)2=2x2-4x+4
f=4x-4=0 x=1 =1 =2-1=1
39. 3 . 1) -1>0 2)x-1<0 3) x=0