The purpose of two questions in the second paragraph is to ________. [A] demonstrate why people are amused [B] display what people laugh at [C] bring to light the phenomenon of laughter [D] accent what a phenomenon laughter really is
【简答题】设定义在R上的函数f(x)=ax 3 +bx 2 +cx+d(a,b,c,d∈R),当x=-1时f(x)取得极大值 2 3 ,且函数y=f(x)为奇函数. (Ⅰ)求函数f(x)的表达式; (Ⅱ)设 x n = 2 n -1 2 n , y m = 2 (1- 3 m ) 3 m (m,n∈ N * ) ,求证: |f( x n )-f( y m )|< 4 3 .