推论 中()②fx=∑fx; i=1 i=1 (2)|(x)=C(x); (3)ⅢIf(x)=f1(x)1(x)…fn(x) i=1 工工工 +…+f1(x)2(x)…f(x) =∑Ⅱf(x)k(x); i=1k=1 ≠i 上页推论 (1) [ ( )] ( ); 1 1   = =  =  n i i n i fi x f x (2) [Cf (x)] = Cf (x); ( ) ( ); ( ) ( ) ( ) (3) [ ( )] ( ) ( ) ( ) 1 1 1 2 1 2 1 =    + +     = =  = = n i n k i k i k n n n i i f x f x f x f x f x f x f x f x f x   