一道很简单的sat数学题!
问题描述：
一道很简单的sat数学题!
The first term in the sequence above us a,and each term after the first is 3 times the preceeding term.If the sum of the first 5 terms is 605,what is the value of
答
a1=n,an=3*a(n-1)
s5=a1+a2+a3+a4+a5=605
a1=5
the value of a is 5