, , , ; , .
, 0 f(x) , 0 , .
, .
, (-,+) 0 ( , = 0) 0, 0 ( ) . :
1) f(x)>0 < 0 f(x)<0 > 0, . . f(x) 0 . , [ 0 -, 0 ] f(x) , a [ 0, 0 + ] , f(x) [ 0 -, 0 + ], . . 0 .
2) f(x)<0 < 0 f(x)>0 > 0, . . f(x) 0 . , 0 .
3) f(x)>0 < 0 > 0 f(x) 0, . . 0, . , ; 0 , f(x)<f(x 0), , f(x)>f(x 0) 0 .
, 0: f(x) < 0, > 0, 0 ; f(x) , , , ; , .
, (,b), , , :
a< 1 < 2 < < k < k+1 < < n <b (3.1)
, , (, 1), ( 1, 2), ,( k, k+1), ,( n,b) f(x) , , f(x) ., f(x) , , ( k, k+1), , k k+1, , (3.1).
: f(x) ( k, k+1) , ( ) - .