题目

There are _____in our school.  A. two hundred teacher    B. two hundred teachers   C. two hundreds              D. two hundreds teachers 答案：B已知{an}为等差数列，且a3=-6，a6=0．（Ⅰ）求{an}的通项公式；（Ⅱ）若等比数列{bn}满足b1=-8，b2=a1+a2+a3，求数列{bn}的前n项和公式．