Question

1,-3,9,-27,81,-243..的规律是什么 某三个相邻的数是-1701,求这三个数

Answer 1

an=(-3)^(n-1)
(-3)^(n-1)+(-3)^n+(-3)^(n+1)=-1701
(-3)^(n-1)*7=-1701
(-3)^(n-1)=-243
n-1=5
n=6
a5=-243,a6=729,a7=-2187