题目

— do you listen to tapes?        —Almost every day. Sometimes I even listen to them at breakfast.        A. How long        B. How much                    C. How many        D. How often 答案：D已知α，β是方程x2-3x-5=0的两根，不解方程，求下列代数式的值：（1）1α+1β；（2）α2+β2；（3）α-β．