. 1) ( ) =
2) ()
y(y)=
n= =
.
. ,,b.
, e>0 d>0,
|f(x,y)-A|<e, (*)
|x-a|<d |y-b|<d ( , ).
, |y-b|<d (*) .
.. 2), f(x,y) y(y),
|y(y)-|£e
.. , |y-b|<d,
= = . ...
, 1) 2), () : =j(),
, , , - :
m= =
: .
.
1. u=f(M) EÌRn. Î. u=f(M) , =f(A) (1)
2. ( ). u=f(M) , {Mk}kÎN , MkÎ MkA k¥ , {f(Mk)}kÎN f(A).
3. ( e d). u=f(M) , "e>0 $d>0 , MÎE r(M,A)<d ( , .. |1- |<d,, |n- |<d) Þ|f(M)-f(A)|<e.
(1) :
=0 (1¢)
(x1,,xn), A(,, ).
Dx1=x1- ,,Dxn=xn- , Du=f(x1,,xn)-f(,, ), (1¢) :
=0 (2)
Dx1,,Dxn- , Du .
.. u=f(x1,,xn) (,, ) , Du0, .
r= , (2) : =0.
r (,, ) ( +Dx1,, +Dxn).
u=f(M) , .
u=f(M) .
u=f(M) .
n=2. u=f(x,y) , A(a,b). =, (,b) . u=f(,y) . u=f(,y) . f(,y) =b, .. =f(a,b), f(x,y) A(a,b) .
|
|
=b, (,b) . u=f(,y) . u=f(x,b) x. f(x,b) x=a, .. =f(a,b), f(x,y) A(a,b) x.
u=f(x,y) A(a,b) , f(x,y) f(a,b), (,) (a,b) , , . , =f(a,b) =f(a,b).
.., f(x,y), A(a,b) , .
.
.
1. , , - .
2. .
u=f(x1,,xn), n- M(x1,,xn), n
x1=j1(t1,..,tm),,xn=jn(t1,..,tm) (2)
F m- P(t1,,tm), (2) .
. ji(P) (i=1,2,..,n) P¢(t¢1,,t¢m) F, f(M) M¢(x¢1,,x¢n)
x¢1=j1(t¢1,..,t¢m),,x¢n=jn(t¢1,..,t¢m),
u=f(j1(t1,..,tm),,jn(t1,..,tm))=f(j1(P),,jn(P)) P¢.
.
( 1- - ). f(x,y) D. 1(x1,y1) 2(x2,y2) f(x1,y1)<0 f(x2,y2)>0, 0(x0,y0), : f(x0,y0)=0.
. f(x,y) D ( ), , .. :
m£f(x,y)£M.
. f(x,y) D. "n D $ n(xn,yn) , |f(xn,yn)|>n (3)
{Mn} , ().
ÎD ( , , D , D.
:
f()=f()f()=f(). (3) ...
. f() D, .
.
. f() EÌRn. f() ,
"e>0 $d=d(e)>0 , " ÎE r(, )<d Þ|f()-f()|<e.
|
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"e>0 $d=d(e)>0 , " (,, ) (,, ) ÎE
| - |<d,, | - |<d Þ|f(,, )-f(,, )|<e.
. f() EÌRn, .