题目

This is one of the happiest days ______ spent in my life. A . that have ever been B . that have never been C . which was ever D . which we have never 答案：A20．二次函数f（x）=ax2+bx+c，（1）若a=2．当x∈[-1，3]时．f（x）最大值不大于7，求b+c的最大值；（2）当|f（x）|≤1对x∈[-1，1]恒成立时，都有|ax+b|≤M对x∈[-1，1]恒成立，求M的最N小值．