. (x) = f (x) , . : .
.
(2.12)
:
,
f (x) = A + a (),(2.13)
a () .
(2.12) (2.13) ,
A y (x), f (x) ,
.. = y (x) + a (Δ ). (2.14)
(2.14) Δ
. (2.15)
(2.15) , , , ..
, .
.
, 0 = 0
= = f (x 0).
= f (x 0),
.
, 0 . , x < 0, y (x) = -1, x > 0 y (x) = 1.
(2.15). df (x) f (x) D x
df (x) = . (2.16)
Δ = dx. f (x)
(2.17)
(2.17) , ( (2.16) ).
(.2.2). f ¢(x) f (x). , N. NB D f (x) = f (x + D x) - f (x) (. .2.1).
f ¢(x) , . , ..
. 1.2.
.
= .
f (x) . :
n - f (n)(x) = (f (n-1)(x))¢.
1. y = n.
y ¢ = nxn -1,
y ¢¢ = n (n -1) xn -2,
|
|
y ¢¢¢ = n (n -1) (n -2) xn -3,
...,
y (k) = n (n -1) (n -2)...(n - k +1) x (n-k) ( £ n).
2. . .
. t
; .
, .
d (df (x)) = (df (x))¢Dx = (f ¢(x)D x)¢D x = f ¢¢(x) (D x)2
.
( t).
t:
,
,
.