题目内容
答案:10 4n-2
解析:由已知得a1-1=1,即a1=2,且nan+1-(n+1)an=2.
可求a2=6,a3=10,a4=14,
归纳得an=2+(n-1)×4=4n-2.
A.3-i B.1+3i C.3+i D.1-3i
A.(x-1)2+4y2=1 B.(x-1)2-4y2=1
C.(x-1)2+y2=1 D.(x-1)2-y2=1