东沟村今年种植柳树与梧桐树的棵数比是5:8,种植柳树的棵数比梧桐树的棵数少____%,种植梧桐树的棵数比柳树多____%。
— _____ will your father return home? It's a long time since I saw him last time.
— Just in two days.
①不等式f(x)≤0的解集有且只有一个元素;
②在定义域内存在0<x1<x2,使得不等式f(x1)>f(x2)成立.设数列{an}的前n项和Sn=f(n).