˲ ֲ
.
1- . .
2- . .
3- . .
5.6.1.
() , , , , , .
, , , , :
) , ;
) f (x) , f (x) = 0 ;
) f (x) j(x). f (j(x)) , j(x) , f (j(x)) . , f (x) = 4cos x R.
) ;
) f (x) j(x) , , f (j(x)) j(x) , f (j(x)) ;
) f (x) , j(x) , , f (x) , j(x) , f (j(x)) j(x) , f (j(x)) . , f (x) = 2 x R, f (x) = 2cos x R, cos x, , cos x.
5.6.2.
1. f(x) [a; b] . f(x) [a; b], , .
. . , , .
. f (x) [ a; b ] . . ³ , f (x) [ 0; ], 0 < x [ ; 0], < x 0.
,
0 . , , , , Î[ a; b ], f (x) , f (x 0) [ a; b ].
5.6.3.
. f (x) (a; b) 0Î(a; b). , f (x) x 0, x 0, f (x) < f (x 0) < x 0, > x 0
f (x) > f (x 0).
f (x) 0Î(a; b), , f (x) > f (x 0) < x 0, f (x) < f (x 0) > x 0.
2 ( ). f(x) 0Î(a; b) f¢(x0) > 0 (f¢(x0) < 0), f(x) () 0.
. , f¢ (x 0) > 0. , 0, ¹ 0. , f (x) < f (x 0) < x 0, f (x) x 0. , f¢ (x 0) < 0.
|
|
3 ( ). f(x) () (a; b), () .
5.6.4.
.
4 ( ). f (x) [ ; b ] (a; b). :
1) f (x) [ ; b ], , Î(a; b);
2) f (x) [ ; b ], , Î(a; b).
. .
. f (x) [ ; b ] f¢ (x) (a; b). , f¢ (x) ³ 0 Î(a; b). - Î(a; b) . , (a; b) f (t) ³ f (x) , , t >
,
,
.
. f (x) [ ; b ] - Î(a; b). 2 1 [ ; b ] 2 > 1. , .
, 1 2 (; b) 2 > 1 f (x 2) ³ f (x 1), f (x) .
5 ( ). f (x) [ ; b ] (a; b). f (x) () [ ; b ], :
1) f¢ (x) ³ 0 (f¢ (x) £ 0) - Î(a; b);
2) f¢ (x) = 0 , [ ; b ].
6 ( ). f (x) [ ; b ] (a; b). f¢ (x) > 0 Î(a; b), f (x) [ ; b ], f¢ (x) < 0 Î(a; b), f (x) [ ; b ].
5.6.5.
1. f¢ (x), f¢ (x) = 0 ( ), (a; b) 1, 2, , k, a < x 1 < x 2 < < xk < b, (; 1), ( 1; 2), , (k 1; k), (k; b).
2. . , f¢ (x) , ; . , f¢ (x) > 0, f (x) , f¢ (x) < 0, f (x) .
6 , , . f (x) [ ; b ] , (a; b) f¢ (x) , [ ; b ] f (x) , f¢ (x) > 0 , f¢ (x) < 0 .
|
|
.
●
,
f¢ (x) Î( ¥; + ¥) = 0, = 1, =3, ( ¥; 0), (0; 1), (1; 3) (3; + ¥) . f¢ ( 1) > 0, , f¢ (2) < 0,
f¢ (5) > 0, f¢ () > 0, Î( ¥; 0), f¢ () > 0, Î(0; 1), f¢ () < 0, Î(1; 3), f¢ () > 0, Î(3; + ¥).
f (x) ( ¥; 0); (0; 1); (3; + ¥) (1; 3).
5.6.6.
f (x) .
. f (x) ( ), 0Î , Î
:
() ( ).
, , . , . , f (x) (), () () .
, .
:
f (x) = 2, Î = { 1, 0, 1, 2, 3}.
● f (x) = f (3) = 9, .
5.6.7.
( )
f (x) [ ; b ] 0 : 0Î(a; b).
. f (x) 0 , 0, , ¹ 0, f (x) £ f (x 0). f (x 0) ( ) f (x) x 0 max f (x) = f (x 0).
f (x) 0 , 0, ( ¹ 0), , f (x) ³ f (x 0). f (x 0) ( ) f (x) 0 min f (x) = f (x 0).
. 5.31
, ¹ 0 0 , f (x) ( ).
ᒺ ( ) .
5.6.8. .
f (x) (a; b).
. (a; b), f¢ (x) (f¢ (x) = 0), f (x) (a; b).
. 0Î(a; b) f (x), (a; b), , = f (x) ( 0; f (x 0)) , .
f (x) [ a; b ] (a; b) , , , .
1. 0 , , , (f¢ (x) = 0) .
.
. f (x), [ ; b ] (a; b) ( , , , f¢ (x) ), , , [ ; b ], , f (x) [ ; b ].
|
|
.
● f¢ (x) = 2 5 + 6. f¢ (x) = 0, = 2 = 3. f (x) , , = 2 = 3.
5.6.9.
f (x) 0, , , 0. , f¢ (x) 0 , 0, f¢ (x) > 0, f¢ (x) < 0. f¢ (x) 0 , 0, f¢ (x) < 0, f¢ (x) > 0.
, f¢ (x) 0 , f¢ (x) ( , 䒺).
2. f (x) 0, , , 0, f (x) . :
1) 0 f¢ (x) , 0 f (x) ;
2) 0 f¢ (x) , 0 f (x) ;