题目

设函数f(x)＝2x，g(x)＝＋2. (1)求函数g(x)的值域； (2)若g(x)≤，求实数x的取值范围； (3)当f(x)＝g(x)时，求2x的值. 答案：解 (1)因为|x|≥0，所以2|x|≥1，所以0<≤1， 所以2<g(x)≤3， 即函数g(x)的值域为(2，3]. (2)由g(x)≤，得2－|x|＋2≤， ∴2－|x|≤，∴|x|≥1，∴x≥1或x≤－1， ∴原不等式的解集为(－∞，－1]∪[1，＋∞). (3)当f(x)＝g(x)时，有2x＝＋2， 当x≥0时，得2x＝＋2，即(2x)2－2·2x＋1＝2，所以(2x－1)2＝2， 得2x－1＝(舍Ⅳ。根据?酋字母或汉语提示完成句子【1】Monkey King is my favourite c_______hero．【2】The man is not only h______，but also very kind．【3】The boy looks very s______．He draws everything well．【4】Yang Liwei is a great space h_______in China．【5】Don’t l_______at people in trouble．【6】He is very h_______．He often makes us laugh．【7】I have a________(打架)with Jim．I hurt him．【8】We’ve decided to teach him a________(教训)．【9】There are many stars in the_________(天空)at night．【10】This pair of shoes is very________(时髦的)．