Вступ до аналізу. Ч. 2
.pdf+ % ':
lim f ( x) = A .
x→ x0
% "-
, $ !.*
& # , " # . .8
" # , # " A , #
« $" %» ( $ , % , %)
y = f ( x ) , # x « $" %» (%) "
x0 . , "% ’" « $" %», «$" %», $ -
$" %, $" % # x "
x0 y = f ( x ) " A . ' δ. 2 $ ,
| x − x0 | < δ , |
(18.1) |
$ # x " % δ-" x0 . ) #
ε . 2 $ ,
| f (x) − A | < ε , |
(18.2) |
$ y = f ( x ) " % ε -" A . |
|
# # %? ,, % #
$" % x x0 , % $" %, , -
" ε . & ' " " ε > 0
" δ > 0 , " % ε , , (18.1) $ -
(18.2). 3 -
.
. 4 " A % y = f ( x ) x → x0
( $ x0 ), " # # " ε -
" δ, " % ε , " $% % x , "% %
% | x − x0 | < δ , x ≠ x0 , % | f (x) − A | < ε .
+ % ': lim f ( x) = A .
x→ x0
+ "% #":
lim f ( x) = A ε > 0 δ(ε) > 0 x : 0 < | x − x0 | < δ | f (x) − A | < ε .
x→ x0
3 $ "%'.
% # « ε − δ », $ " # . 0 # " . 38. % # , # x " %
( x0 − δ, x0 + δ ) , $ 0 < | x − x0 | < δ , y = f ( x) " %
( A − ε, A + ε) , $ | f (x) − A | < ε .
* 0 0 1 (1821–1881) – % . 0 0.
67
*. 38.
!. $ ! " # .
. A = lim f ( x) 5 '. ε > 0 δ(ε) > 0
|
x→ x0 |
|
x : 0 < | x − x0 | < δ | |
f (x) − A | < ε . ,$ "% ε > 0 |
#" |
"% " % |
{xn} % # x , |
lim xn = x0 . |
|
n → ∞ |
" % # ε % N , n > N | xn − x0 | < δ . ! | f ( xn ) − A | < ε . '", ε > 0 N n > N -
: | f ( xn ) − A | < ε . 2 , lim |
f ( xn ) = A , $ A = lim f ( x) |
n → ∞ |
x→ x0 |
0. |
|
A = lim f ( x) 0. , " A #-
x→ x0
y = f (x) 5 '. , . ε > 0δ > 0 : 0 < | x − x0 | < δ | f (x) − A | ≥ ε . $ " % {xn} -
% # x , lim xn = x0 . |
lim f ( xn ) = A , $ : |
n → ∞ |
n → ∞ |
δ > 0 N1 n > N1 : | xn − x0 | < δ ,
ε > 0 N2 n > N2 : | f ( xn ) − A | < ε .
:
ε > 0 δ > 0 : 0 < | x − x0 | < δ | f (x) − A | ≥ ε .
/ x x = xn , . , A = lim f ( x)
x→ x0
5 '.
.
.
1. ), lim x2 = 4 . 5 '. -
x→2
"% ε > 0 #":
68
x2 − 4 = ( x − 2 + 2)2 − 4 = ( x − 2)2 + 4( x − 2) + 4 − 4 ≤ x − 2 2 + 4 x − 2 .
| x − 2 | < δ . | x2 − 4 | < δ2 + 4δ . #, $
$ ', ε ( | x2 − 4 | $"%' $ ', ε ), $ δ2 + 4δ < ε . *’ ( , δ > 0 )
" (0, 4 + ε − 2) . , $ δ < 4 + ε − 2 ( $
ε '" δ ), $ | x2 − 4 | < ε . + δ $% " " (0, 4 + ε − 2) , "
δ= 1 + ε 4 −1.
2.), lim x2 − 1 = 2 .
x→1 x − 1
5 '. "% ε > 0 #"
x ≠ 1:
x2 − 1 |
− 2 |
= |
|
( x − 1)( x + 1) |
− 2 |
= |
|
x + 1 − 2 |
|
= |
|
x − 1 |
|
. |
|
|
|
|
|
|
|||||||||||
x − 1 |
|
|
x − 1 |
|
|
|
|
||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
/ 0 < | x −1| < δ , , $ δ < ε (" δ = ε2 ), $
|
|
x2 − 1 |
|
< ε , $ $" . |
|
||||||||||
x −1 |
|
||||||||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
3. ), y = sin |
1 |
# x → 0 . 3- |
||||||||||||
|
x |
||||||||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
% 0. * #" " % {xn } , |
|||||||||||||||
x = |
1 |
. ,, lim x = 0 . : |
|
|
|
|
|
||||||||
|
|
|
|
|
|
||||||||||
n |
|
πn |
|
|
n→∞ |
n |
|
|
|
|
|
|
|
||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
lim f (xn ) = lim sin πn = lim 0 = 0 . |
|
|
|
|
|
|
|
||||||||
n→∞ |
n→∞ |
n→∞ |
|
|
|
|
|
|
|
|
|
|
|||
|
|
|
|
|
|
|
|
|
% |
|
% |
|
2 |
|
|
|
#" ' " % {xn } , |
xn = |
|
. |
|
||||||||||
|
π(4n + 1) |
||||||||||||||
|
% |
|
|
|
% |
|
|
π(4n + 1) |
|
|
|
|
|||
lim xn = 0 . !" % # lim f (xn ) = lim sin |
|
|
= lim1 = 1. |
|
|||||||||||
2 |
|
|
|||||||||||||
n→∞ |
|
|
n→∞ |
n→∞ |
|
|
n→∞ |
|
|||||||
|
|
|
|
|
|
,, " " % #,
", " % % # – 0 1. &
, # 0, ' # x → 0 .
", " ' #
y = f ( x) x0 . 3
# : $ , $ $" x ≠ x0 ; $ , , x − x0 > 0 . " 2 , # , " -
69
# " x0 , !", % , "
x0 , # $ ’
. * #" "% ' " .8.
1, x ≠ 0, f ( x) =
0, x = 0.
), lim f ( x) = 1. ε > 0 #" " $% x ≠ 0 :
x→0
| f (x) −1| = |1 −1| = 0 < ε $ δ $% - ". * f (0) = 0 .
- $ , " x0 , #
. * #", ", :
|
|
1 |
|
f ( x ) = sin |
|
, x ≠ 0, |
|
x |
|||
|
1, |
x = 0. |
|
|
2 x = 0 , # ( . - " 3).
# # x "
# " x0 . !" % -
( # %, ", , "
#" % " %).
:
. 4 " A % y = f ( x) x → ∞ ,
" $% # " ε > 0 " M = M (ε) > 0 , -
| x | > M " % | f (x) − A | < ε .
':
lim f ( x) = A.
x→∞
2 $" % # ",
$" % #.
3 # $ .
. 5 %, y = f ( x) x → x0
, " $% # # " E
" δ = δ(E) , 0 < x − x0 < δ " -
% f ( x ) > E .
': lim f (x) = ∞ .
x→x0
70
$ % $" % # x " x0
y = f ( x) $ $" " $"%', $% -
" E .
+ % y = f ( x) %
x0 . |
|
|
. ), y = |
1 |
" |
|
||
|
x −1 |
x= 1 .
"% E > 0 #":
f ( x ) |
|
= |
|
1 |
|
= |
|
1 |
|
|
. |
|
|
|
|
||||||||||
|
|
|
|
|
|
|
|
|
||||
|
x −1 |
|
|
x −1 |
|
|
||||||
|
|
|
|
|||||||||
|
|
|
|
|
|
|
|
|
|
|||
|
|
|
|
|
|
|
|
|
|
|
|
|
/ 0 < | x −1| < δ , | f ( x) | > |
1 |
. #, $ |
1 |
> E , $ δ < |
1 |
. |
|||||||
|
|
|
|
|
|||||||||
|
|
δ |
|
|
δ |
|
|
|
E |
||||
", δ = |
1 |
. E '" δ = |
1 |
, |
|||||||||
|
|
||||||||||||
|
2E |
|
|
|
|
|
2E |
||||||
0 < | x −1| < δ " % |
|
f ( x ) |
|
> E , $ |
|||||||||
|
|
||||||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
lim f ( x) = ∞ .
x→1
0 , -
.
. 5 %, lim f ( x ) = +∞ |
(lim f ( x ) = −∞), |
|||||||
|
|
|
x→x |
x→x |
||||
|
|
|
0 |
|
|
|
|
0 |
E > 0 δ(E) > 0 : 0 < | x − x0 | < δ f ( x) > E ( f ( x) < −E ) . |
||||||||
": lim |
1 |
= +∞ ; |
|
|
= −∞ . |
|
||
lim ln |
|
x |
|
|
||||
|
|
|||||||
x→x0 x2 |
x→0 |
|
|
|
|
|
||
|
|
|
||||||
". 3 " # |
y = f ( x) # x → ∞ , $ lim f ( x) = ∞ .
x→∞
$ # % .
. 4 " A % y = f ( x)
x → x0 , ε > 0 δ = δ(ε) > 0 : 0 <| x − x0 | < δ, x < x0 | f ( x) − A | < ε .
+ % ': lim f ( x) = A .
x→ x0 − 0
. 4 " A % y = f ( x)
x → x0 , ε > 0 δ = δ(ε) > 0 : 0 <| x − x0 | < δ, x > x0 | f ( x) − A | < ε .
+ % ': lim f ( x) = A .
x→ x0 + 0
$ ' x x0 , " ' % % - ', x0 , # – " ' % % $"%', x0 .
71
0 " y = f ( x) x0 %
.
.
−1, x < 0,
1. y = sgn x = 0, x = 0,
1, x > 0.
, lim sgn x = −1, |
lim sgn x = 1 . 3 #" - |
x→−0 |
x→+0 |
x < 0 . "% ε > 0 ε δ > 0 , -
−δ < x < 0 $ " % sgn x − (−1) < ε . ),
−δ < x < 0 , sgn x − (−1) = sgn x + 1 = −1 + 1 = 0 , $ δ
$% ". lim sgn x = −1. ! " # -
|
|
|
|
|
|
|
|
|
|
|
|
x→−0 |
|
|
|
|
|
|
|||
, |
lim sgn x = 1. |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|||||
|
|
|
|
x→+0 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
||
2. , lim |
1 |
|
= −∞ , |
1 |
|
= +∞ . |
|
||||||||||||||
|
|
|
lim |
|
|
|
|||||||||||||||
|
|
|
|
|
|||||||||||||||||
|
|
|
|
|
x→1−0 x −1 |
|
|
|
x→1+0 x −1 |
|
|
|
|
|
|
||||||
x < 1 . |
|
"% E > 0 , |
|||||||||||||||||||
δ = δ(E) > 0 , 1 − δ < x < 1 |
$ " |
1 |
|
< −E . ), |
|||||||||||||||||
x −1 |
|||||||||||||||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|||||
"% 0 < 1 − x < δ , |
|
1 |
|
> |
1 |
> E , "% δ < |
1 |
. ! "- |
|||||||||||||
1 − x |
|
|
|||||||||||||||||||
|
|
|
|
|
|
|
δ |
|
|
|
|
|
E |
|
|||||||
, |
1 |
|
< −E , $ $" . ! " # %, |
||||||||||||||||||
|
|
|
|||||||||||||||||||
|
|
x −1 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
||||
1 |
|
= +∞ . |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
||||
lim |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|||||
x→1+0 x −1 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
||||
, lim f (x ) = A, lim |
f ( x) = B , # " % |
||||||||||||||||||||
|
|
|
|
|
x→x0 −0 |
|
|
|
|
x→x0 +0 |
|
|
|
|
|
|
|
|
|
. 39.
*. 39.
72
!. % lim f ( x ) = A , -
x→x0
x0 , A .
. lim f ( x ) = A. ε > 0 δ > 0 :
x→x0
0 < | x − x0 | < δ | f ( x) − A | < ε . 2 , % f ( x ) − A < ε
% " x (x0 − δ , x0 ) , " x (x0 , x0 + δ ). ! #
$ # % , lim |
f ( x) = lim f (x) = A . |
||||||
|
|
|
|
|
|
x→x0 −0 |
x→x0 +0 |
|
lim |
f ( x) = lim f (x) = A . ε > 0 δ1 (ε ) > 0 : |
|||||
|
x→x0 −0 |
|
|
x→x0 +0 |
|
||
x0 − δ < x < x0 |
|
|
f ( x ) − A |
|
< ε . ! δ2 (ε ) > 0 : x0 < x < x0 + δ |
||
|
|
f ( x ) − A < ε . %
$ % f
.
δ = min (δ1 ,δ2 ) . 0 < x − x0 < δ ,
( x ) − A < ε , , lim f (x ) = A. -
x→x0
19. # .
# ’ "
.
. . y = α(x) % x → x0 ,
lim α( x) = 0 .
x → x0
$ , ε > 0 δ(ε) > 0 : 0 < | x − x0 | < δ | α( x) | < ε .
! " # % , " x → ∞ .
", y = (x −1)2 – " x → 1, y = sin x –
" x → 0 , y = 1 – " x → ∞ . x
!. & ' y = α(x) y = β(x) x → x0 ,
y = α( x) ± β( x), y = α( x)β( x) –
x → x0 .
. ) " ' " ("
$ % " #, $% ). ,, "%
y = α (x) – " x → x0 , ε > 0 δ1 (ε ) > 0 :
73
|
|
|
|
|
|
|
|
α |
( x ) |
|
< |
ε |
. ! "% y = β ( x) |
– " |
||||||||||||||||||||||||||||||||
0 < |
|
x − x |
|
< δ |
1 |
|
|
|||||||||||||||||||||||||||||||||||||||
|
|
|||||||||||||||||||||||||||||||||||||||||||||
|
|
|
|
|||||||||||||||||||||||||||||||||||||||||||
|
|
|
0 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
ε |
|
|
|||
|
x → x , ε > 0 δ |
|
|
|
(ε ) > 0 : |
|
|
|
|
|
< δ |
|
|
|
β ( x ) |
|
< |
. |
/ |
|||||||||||||||||||||||||||
|
2 |
0 < |
|
x − x |
|
2 |
|
|
||||||||||||||||||||||||||||||||||||||
|
|
|||||||||||||||||||||||||||||||||||||||||||||
|
|
|
|
|
||||||||||||||||||||||||||||||||||||||||||
0 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
0 |
|
|
|
|
|
|
|
|
2 |
|
|
|||||||
" δ = min (δ1 ,δ2 ) , 0 < |
|
|
|
|
|
|
|
|
|
|||||||||||||||||||||||||||||||||||||
x − x0 |
< δ $ ", |
|||||||||||||||||||||||||||||||||||||||||||||
|
|
α ( x ) |
|
|
< |
ε |
|
|
|
|
|
|
β ( x ) |
|
< |
ε |
|
. |
|
|
|
|
|
|
|
|
|
|
|
|
|
|||||||||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
||||||||||||||||||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|||||||||||||||||||||||||||
|
|
|
|
|
|
|
|
|
|
|
|
2 |
|
|
|
|
|
|
|
|
2 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|||||||||||
|
α ( x ) + β ( x ) |
|
≤ |
|
α ( x ) |
|
+ |
|
β ( x ) |
|
< |
ε |
+ |
ε |
= ε , |
|
|
|
||||||||||||||||||||||||||||
|
|
|
|
|
|
|||||||||||||||||||||||||||||||||||||||||
|
|
|
|
|
|
|
|
|
||||||||||||||||||||||||||||||||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2 |
2 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
y = α ( x) + β (x ) – " x → x0 .
, , ", # " "
"..
". 4 " $ ’ -
". ". * #"
y |
|
= x , |
y |
2 |
= x2 . ,$ " |
x → 0 . !" |
||
1 |
|
|
|
|
|
|
||
y1 |
= |
x |
= |
1 |
" x → 0 . |
|
||
y |
2 |
x2 |
x |
|
||||
|
|
|
|
|
||||
|
|
|
|
|
|
|
|
!. ( -
.
. |
|
y = f ( x) $ x → x0 , |
|
||||||||||||||||
y = α ( x) |
|
– " x → x0 . δ1 -" x0 |
|||||||||||||||||
|
|
|
|
|
|
f ( x ) |
|
|
|
|
|||||||||
% % |
|
≤ M , M > 0 . 5 # ε > 0 δ2 > 0: |
|||||||||||||||||
|
|
|
|
|
|
α ( x ) |
|
ε |
|
|
(δ |
|
|
) , |
|||||
0 < |
|
x − x |
|
< δ |
2 |
|
< |
. / 0 < |
x − x |
< δ = min |
,δ |
2 |
|||||||
|
|
||||||||||||||||||
|
|
|
|
||||||||||||||||
|
|
0 |
|
|
|
|
|
|
M |
|
0 |
|
1 |
|
|
||||
: |
|
|
|
|
|
|
|
|
|
|
|
|
|||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
f ( x )α ( x ) = f ( x ) α ( x ) < M ε = ε ,
M
$ f ( x)α ( x) – " x → x0 .
, $ " " -
".
!. |
& ' y = α ( x) – x → x0 , - |
||||
y = |
|
1 |
– x → x0 . ) , ' |
||
|
|
||||
|
( x) |
||||
α |
|
|
|
||
y = f (x) x → x0 , y = |
1 |
– - |
|||
|
|||||
|
f ( x)
x → x0 .
74
|
|
. |
|
α |
(x) |
– |
" |
x → x0 . |
|
||||||||||||||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
< δ |
|
α ( x ) |
|
< ε . "% |
|
* #- |
||||||||||
ε > 0 δ > 0 : 0 < |
|
x − x0 |
|
|
|
E > 0 . |
|||||||||||||||||||||||
|
|
||||||||||||||||||||||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|||||||
" 0 < |
x − x0 |
< δ : |
|
|
|
|
|
|
|
|
|
|
|
|
|||||||||||||||
|
|
|
|
= |
|
1 |
> |
1 |
= E , |
$ ε = |
1 |
. |
2 |
, |
|
||||||||||||||
|
|
1 |
|
|
|
||||||||||||||||||||||||
|
α ( x ) |
|
|
|
α ( x ) |
|
|
||||||||||||||||||||||
|
|
|
|
|
|
|
ε |
|
|
|
|
|
|
E |
|
|
|
|
|||||||||||
|
y = |
1 |
|
|
|
– " x → x0 . |
|
|
|
|
|||||||||||||||||||
|
|
|
|
|
|
|
|
|
|
|
|||||||||||||||||||
α( x) |
|
|
|
|
|||||||||||||||||||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
) # % " #.
20. $ % .
$% 1. & ' y = f (x) x → x0 ,
.
. , y = f ( x) x0 #
A B , A ≠ B . A − B > 0 . , "% lim f (x ) = A,
x→x0
ε > 0 δ1(ε) > 0 : 0 < | x − x0 | < δ1 | f ( x) − A | < ε . ! "%
lim f (x ) = B , ε > 0 δ2 (ε) > 0 : 0 < | x − x0 | < δ2 | f ( x) − B | < ε . -
x→x0
δ = min(δ1, δ2 ) . , | x − x0 | < δ , $% -
% | f (x) − A | < ε , | f (x) − B | < ε . , "% - % " $% # # ε , ", ", ε = | A − B |2 .
:
0 < A − B = A − f ( x ) + f ( x ) − B ≤ f ( x ) − A + f ( x ) − B <
< ε + ε = 2ε =| A − B | ,
$ " A − B ' # $ , ". , -
" ' #.
$% 2. & ' lim f ( x) = A δ > 0 -
|
x → x0 |
|
, ' ( x0 − δ, x0 ) ( x0 , x0 + δ) |
y = f ( x) . |
|
. lim f ( x) = A . |
ε > 0 δ > 0 : |
0 < | x − x0 | < δ |
x → x0 |
|
|
| f ( x) − A | < ε . , ( x0 − δ, x0 ) ( x0 , x0 + δ) |
: |
| f (x) | = | A + f (x) − A | ≤ | A | + | f (x) − A | < | A | + ε ,
, y = f ( x) $ .
75
$% 3. & ' lim f ( x) = A , A ≠ 0 , δ > 0 , '
x → x0
( x0 − δ, x0 ) ( x0 , x0 + δ) y = f ( x) ! , ' !
A .
. , "% |
lim f ( x) = A , ε > 0 δ > 0 : 0 < | x − x0 | < δ |
|
x → x0 |
| f ( x) − A | < ε . !$ |
|
A − ε < f (x) < A + ε . |
(20.1) |
, "% A ≠ 0 , A > 0 $ A < 0 . / A < 0 , $ ε "% - |
|
", $ " |
A + ε < 0 . (20.1) - |
", f ( x) < 0 . / A > 0 , $ ε "% ", $ - |
|
" A − ε > 0 . |
" (20.1) ", |
f ( x) > 0 . ( x0 − δ, x0 ) ( x0 , x0 + δ) |
y = f ( x) |
||||
$# " A . |
|
|
|
||
2 " % % " . |
|
||||
$% 4. & ' |
lim g ( x) = B , B ≠ 0 , δ > 0 , ' |
||||
|
|
|
x → x0 |
|
|
1 g ( x) |
( x0 − δ, x0 ) ( x0 , x0 + δ) . |
|
|||
. |
, "% |
lim g( x) = B , ε > 0 δ > 0 : 0 < | x − x0 | < δ |
|||
|
|
|
x → x0 |
|
|
| g(x) − B | < ε . |
" ε = | B | 2 . |
, "% | g(x) − B | ≥ | B | − | g(x) | , |
|||
| B | − | g ( x) | < | B | |
2 , | g ( x) | > | B | |
2 , 1 | g ( x) | < 2 | B | , "% |
|||
x ( x0 − δ, x0 ) ( x0 , x0 + δ) , $ 1 g ( x) $ |
|
( x0 − δ, x0 ) ( x0 , x0 + δ) .
$% 5 ( «* »). & ' δ > 0 , '
x ( x0 − δ, x0 ) ( x0 , x0 + δ) |
: |
|
g( x) ≤ f (x) ≤ h( x) , |
(20.2) |
|
' |
|
|
lim |
g( x) = lim h( x) = A , |
(20.3) |
x → x0 |
x → x0 |
|
lim f ( x) = A .
x → x0
. 3 % # 0.
{xn} – |
"% " % % # x , n : |
xn ( x0 − δ, x0 ) ( x0 , x0 + δ) , lim xn = x0 . " (20.3): |
|
|
n → ∞ |
lim g( xn ) = lim h( xn ) = A . |
|
n → ∞ |
n → ∞ |
" (20.2) : g ( xn ) ≤ f ( xn ) ≤ h( xn ) .
76