题目

 Hearing his father was seriously ill, ___________.    A. he burst into tears                         B. his eyes were filled with tears    C. his face lost its color                       D. tears came to his eyes 答案：A已知函数g(x)=-(12)x2的值域为A，定义在A上的函数f（x）=x-2-x2（x∈A）．（1）求集合A，并判断函数f（x）的奇偶性；（2）判断函数f（x）的单调性，并用单调性定义证明；（3）解不等式f（3x+1）＜f（5x+1）．