1
= f (x) () (,b), 1 < 2, 1, 2 Î (, b) f (1) < f (2) ( f (1) > f (2)).
1
1) f(x), [a, b], , [a, b] , . . f'(x)>0.
2) f(x) [a, b] (a, b), f'(x)>0 a<x<b, [, b].
. . f(x) [ a, b ]. x ∆ x
f(x) - , f(x+∆ x) > f(x) ∆ x >0 f(x+ ∆x) < f(x) ∆x >0.
> 0
, ,
> 0
. . f'(x) >0, . ( f'(x)< 0, ∆x (1) , (2).)
. f'(x) >0 x, (a, b).
x 1 x 2, x 1 < x 2,
[ , b ].
f(x 2 ) - f(x 1 ) = f' (x) (x 2 x 1 ), x 1< x < x 2.
f' (x)>0, , f(x 2 ) - f(x 1 ) >0, , f(x)‒ .
() , : f(x) [ , b ], f'(x) < 0 . f'(x) <0 (a, b), f(x) [ , b ]. (, , [ , b ] (a, b).)
. . [ , b ] f(x) , y= f(x) 0 ; . y= f(x) [ , b ], ‒ ( ( ) ); .
f (x) ( ). , f'(x) = 0 f'(x) .