Вступ до аналізу. Ч. 2
.pdf! # « "» " " ( . . 10) ", lim f ( xn ) = A . & # #
n → ∞
0 , lim |
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x → x0 |
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δ > 0 : 0 < | x − x0 | < δ f (x) ≤ g (x) ( $ |
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lim g( x) = B , A ≤ B . |
x → x0 |
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0 " # % ". $% 7 ( , ' -
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x → x0 , * , ' f ( x ) = A + α ( x ) ,
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. lim f ( x ) = A .
x→x0
ε > 0 δ = δ (ε) > 0 : 0 < x − x0 < δ f ( x ) − A < ε . 2 , -
α ( x ) = f ( x ) − A " x → x0 . !
f ( x ) = A + α ( x ) , α ( x ) – " x → x0 .
, f ( x ) = A + α ( x ) , α ( x ) – "
x → x0 . ε > 0 δ (ε) > 0 : 0 < x − x0 < δ α ( x ) < ε . $
f ( x ) − A < ε , , lim f ( x ) = A . .
x→x0
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lim g ( x ) = B . , |
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lim f ( x ) g ( x ) = AB , |
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x→x0 g ( x) |
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f ( x ) = A + α ( x ), g ( x ) = B + β( x ), α ( x ), β ( x ) – "
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: lim ( f ( x ) ± g ( x )) = A ± B .
x→x0
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77
" Bα ( x ) , Aβ ( x ), α ( x )β ( x ) – " x → x0 ,
lim f ( x ) g ( x ) .
x→x0
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Bα ( x) − Aβ( x) |
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g ( x) |
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ε > 0 δ2 = δ2 (ε) > 0 : 0 < |
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δ = min (δ1 , δ2 ) , $ ε < | B | 2 . - |
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Bα ( x ) − Aβ( x) |
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< |
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Bα ( x) |
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+ |
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Aβ( x) |
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< |
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B |
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ε + |
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A |
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ε |
= |
2 ( |
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B |
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+ |
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A |
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ε . |
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B (B + β( x)) |
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B2 2 |
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B2 2 |
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B2 |
! "% ε – $% # " ", #
" 2 ( B + A ) ε $ # ", $ - |
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B2 |
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', $% , ". 2 $ . , |
||
lim |
f ( f ) |
= A . |
x→x0 |
g ( x) |
B |
.
, y = C – " , # lim y = C , $
x→x0
". % # # $
" " %:
lim |
(Cf ( x )) = C lim f ( x ) , |
x→x0 |
x→x0 |
$ ! .
. ,$"
lim |
3x2 |
− 5x + 6 |
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. |
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3 |
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x→2 |
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+ x + 1 |
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78
- :
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3x |
2 |
− 5x + 6 |
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lim (3x2 − 5x + 6) |
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3lim x2 − 5 lim x + lim 6 |
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lim |
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= |
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x→2 |
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x→2 |
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x→2 |
x→2 |
= |
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( |
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x→2 |
x3 + x +1 |
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lim |
x |
3 |
+ x |
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lim x3 + lim x + lim1 |
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+1 |
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x→2 |
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x→2 |
x→2 |
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3 22 |
− 5 2 + 6 |
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8 |
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23 |
+ 2 + 1 |
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11 |
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21. . |
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& & ' . |
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!. & ' y = f ( x) [a,b] , |
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x0 (a, b) |
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lim |
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f ( x) , |
lim |
f ( x) , |
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x→ x0 +0 |
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x→ x0 −0 |
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lim |
f ( x) , lim |
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f ( x) . |
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x→ b−0 |
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x→ a +0 |
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. " y = f ( x) |
[a,b] . |
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x0 (a, b] . x [a, x0 ) : |
f ( x) < f ( x0 ) . , |
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% y = f ( x) " |
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[a, x0 ) $ , - |
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% # |
sup |
f ( x) = M , M ≤ f ( x0 ) . |
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[a, x0 ) |
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# % # :
) x [a, x0 ) : f ( x) ≤ M ,
$) ε > 0 xε [a, x0 ) : M − ε < f ( xε ) .
δ = x0 − xε > 0 . / x ( xε , x0 ) , x ( x0 − δ, x0 ) , "% -
y = f (x) , f ( xε ) < f ( x) . ε > 0 δ > 0 :x ( x0 − δ, x0 ) f ( x) (M − ε, M ) . # # "
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lim f ( x) = M . ! " # % |
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x→ x0 −0 |
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lim f ( x) , lim |
f ( x) = inf f ( x) . |
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x→ x0 + 0 |
x→ x0 + 0 |
( x0 ,b] |
. 6 , y = f (x) "%
x = x0 " #, " x0 ,
", $ , x0 , , #
ε > 0 δ > 0 x′, x′′ : 0 <| x′ − x0 | < δ, 0 < | x′′ − x0 | < δ | f ( x′) − f ( x′′) | < ε .
$ % $" % % # x0
# $ #
$" %.
(. + * ! δ > 0 , ' y = f ( x) δ-
x0 , , x0 , * !
{xn} , , , '
79
lim xn = x0 , { f ( xn )} . , |
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n → ∞ |
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{xn} . |
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n |
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lim x′ |
= lim x′′ = x . + " %: |
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n → ∞ |
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n → ∞ |
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0 |
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x1, |
x1, x2 |
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, xn ,... . |
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xk . ,, lim x%k = x0 , , |
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k - " " |
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% |
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k → ∞
#, " " {x%k } " % δ-" x0 . #-
" # lim f ( x%k ) = A . ! "% "-
k → ∞
{ f ( xn )}, { f |
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′ |
lim f ( x′ ) = lim |
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n → ∞ |
n |
n → ∞ |
( xn′′ )} " " { f ( x%k )},
f ( x′′ ) = A .
n
7 .
! (! " #). ( , '
lim |
f ( x) , * , ' y = f ( x) - |
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x→ x0 |
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x0 " #. |
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. $%. |
lim |
f ( x) = A . |
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x→ x0 |
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ε > 0 δ > 0 : 0 < | x − x | < δ | f (x) − A | < |
ε |
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x′, x′′ , |
0 < | x′ − x |
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| f (x ) − f ( x ) | = | f (x ) − A + A − f (x ) | ≤ | |
f (x ) |
− A | + | f (x |
) − A | < + = ε . |
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2 |
2 |
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) %. 5 '. {xn} – "% "-
%, , xn ( x0 − δ, x0 ) ( x0 , x0 + δ) , lim xn = x0 . , -
n → ∞
" % { f ( xn )} #, " % $ -
" {xn} .
# 5 ' :
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ε > 0 |
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− x0 |
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− x0 | < δ |
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′′ |
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δ > 0 : 0 < | x |
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| f ( x ) − f ( x |
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, "% |
lim xn = x0 , δ N , |
n > N - |
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n → ∞ |
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: | xn − x0 | < δ . $ |
n > N , m > N : | xn − x0 | < δ , |
| xm − x0 | < δ , |
| f ( xn ) − f ( xm ) | < ε . , " % { f ( xn )} "%, #
5 ' " " #. "
" # " % $ " {xn} . , #
# 0 lim f ( x) .
x→ x0
.
80
22. # % .
* #" # "% .
*. 40.
/ #, $ . 40 ($, ,#),
#, $# . 40( )? - , # . 40( ) "% ", , # . 40 ($, ,#) "%
" . & ' ", # . 40( ) , -
" , # . 40($, ,#) $ "-.
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y = f ( x) , , x0 " "-
, % " ". ' -
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81
% $ x0 . y = h ( x )
% x → x0 . ! y = ϕ( x)
x0 , $ #.
" $% " ,
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1. " % # p h - % $ ":
p= p0 e− kh ,
p0 , k – ". 0 #"
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6, "% ", $ # 40( ).
2. , " % " # " R
T $" " , " T T0 ( " # "). / T < T0 , R -
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% , $" % $" # ". " " "-
1, 2 # ' " 5 "%. 6" % % # , " #
( %; ", " # # " " 2,19 # ' " 5 "%) % ’%.
3 " % " # " -
. 42.
*. 42.
3. " % # "% # # T % -
":
82
ρ= K ,
T
K – ". 0 " #":
*. 43.
$ # 40( ). & % 40(#).
% , " $ " -
" ' , " # $ , , "
% " $ . !" " "% , "
. ,
.
. . y = f ( x) % x0 ,
:
1)" x0 ,
2)lim f ( x ) ,
x→x0
3) lim f ( x) = f (x0 ).
x→x0
/ # « ε − δ »,
" :
. y = f ( x ) % x0 , -
x0 , ε > 0 δ = δ (ε) > 0: x − x0 < δ f (x ) − f (x0 ) < ε .
% #: # $",
", $" , x ≠ x0 , $ x − x0 > 0 . $ #"
$ x0 . & % , "
, # , , $ ’
f (x0 ). + $" %. .
x0 , # x → x0 -
x0 .
, x0 = lim x ,
x→x0
:
lim f ( x ) = f (lim x ). |
|
x→x |
x→x |
0 |
0 |
$ .
83
- ' .
x x − x0 " x0 .
/ x → x0 , |
x → 0 . * % |
f ( x) − f ( x0 ) = f |
( x0 + x) − f ( x0 ) % |
x0 % |
y ( . 44). |
*. 44.
, "% lim f ( x) = f ( x0 ) , lim f ( x) − f ( x0 ) = |
|
x→x0 |
x→x0 |
= lim |
f ( x ) − lim |
f ( x0 ) = lim ( f ( x ) − f ( x0 )) = lim y = 0 . |
|
x→x0 |
x→x0 |
x→x0 |
x→ 0 |
, % x0 , -
" # "
.
0 x0 , "
x0 # "% ".
.
1. ), y = x2 $% " -
.
% "% x " x . -
:
y = ( x + x)2 − x2 = x2 + 2x x + x2 − x2 = 2x x + x2 .
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x → 0 $ $ |
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– " $ |
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84
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f (x) = |
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x = 0 .
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0 ≤ | f (x) − f (0) | = | f (x) | ≤ | x | ,
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x = 0 .
3.),
−1, x < 0,
y = sgn x = 0, x = 0,
1, x > 0
x = 0 .
# x = 0 "
x . :
y = f ( x + x) − f (x ) = f ( x) − f (0) = 1 − 0 = 1,
" " x → 0 . , '
x = 0 .
., , % ", " %
" " # % ( . . 20). $% 1. & ' y = f ( x) x0 , -
x0 .
$% 2. & ' y = f ( x) x0 ,
f ( x0 ) ≠ 0 , x0 , y = f ( x)
f ( x0 ) .
$% 3. & ' f (x) , g ( x) x0 , -
f (x) ± g( x) , f ( x)g( x) x0 . & ' g ( x0 ) ≠ 0 ,
f ( x) g ( x) x0 .
$% 4 ( ). + * ! y = f (x)
x0 , y0 = f ( x0 ) , z = g ( y)
y0 , z = F (x) = g( f ( x)) x0 .
. x0 x . y = f ( x)
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y = f ( x0 + |
x) − f ( x0 ) . . z = g( y) # |
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z = g ( y0 + |
y) − g ( y0 ) . , "% y = f ( x) - |
x0 , lim y = 0 . ! "% z = g ( y) - |
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lim |
z = lim (F ( x0 + |
x) − F ( x0 )) = lim ( g ( f ( x0 + x)) − g ( f ( x0 )) = |
x→ 0 |
x→ 0 |
x→ 0 |
= lim ( g ( y0 + |
y) − g( y0 )) = lim ( g( y0 + |
y) − g ( y0 )) = lim z = 0 , |
x→ 0 |
y→ 0 |
y→ 0 |
$ z = F (x) x0 .
" # $ # % $ -
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. . y = f ( x) % x0 ,
δ > 0 , y = f ( x) " ( x0 − δ, x0 ] ,
lim f ( x) = f (x0 ) . . y = f ( x) % -
x→ x0 −0
x0 , δ > 0 , y = f ( x) -
" [ x0 , x0 |
+ δ) , lim f (x) = f ( x0 ) . |
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x→ x0 + 0 |
23. $ , .
. . y = f ( x) % X ,
X .
, y = f ( x) % (a,b) ,
" (a,b) . . y = f (x) -
% [a,b] , "
(a, b) , , #, a " b .
’%, " , ,
% " , "% " $
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) ' $* '. & ' y = f ( x) -
[a,b] , [a,b] .
. ", $ , M > 0
x0 [a, b] : | f ( x0 ) | > M . , M = 1, x1 [a, b] : | f ( x1 ) | >1.
/ M = 2 , x2 [a, b] :| f ( x2 ) | > 2 . & # " n xn [a, b] :
| f ( xn ) | > n .
" % {xn } $ , "% " " %
[a,b] . " 6 "%–' " $ -
" % {xn |
} : a ≤ xn |
≤ b , lim xn |
= c . !" c [a, b] (" 3 - |
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4, . 10). , "% y = f (x) [a,b] ,
c ,
lim f ( xn |
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k → ∞ |
k |
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!" f ( xn ) > nk . , "% lim nk |
= ∞ , lim f ( xn |
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k |
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86 |
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