已知数列{an}:a1=1,a2=2,a3=r,an+3=an+2(n是正整数),与数列{bn}:b1=1,b2=0,b3=-1,b4=0,bn+4=bn(n是正整数).记Tn=b1a1+b2a2+b3a3+…+bnan.(1)若a1+a2+a3+…+a12=64,求r的值;(2)求证:当n是
下列商品粮基地同时又属于甘蔗产区的是 A．珠江三角洲 B．江淮地区 C．太湖平原 D．三江平原
I called Mary many times yesterday evening, but I couldn' t get through. Her brother on the phone all the time! A. has been talking B. has talked C. t
已知a＞1，下列各式正确的是（ ） A．＞a B．＞（）2 C．＜ D．a＞
two exams to worry about, I have to work really hard this weekend. A. With B. BesidesC. As for D. Because of
已知弧长为π cm的弧所对的圆心角为，则这条弧所在的扇形面积为_______．
