Algebra 2
posted by Tifini .
The simple formula for the nth term of an arithmetic sequence is an = 4n + 16. What is the explicit formula corresponding to the simple formula?

1 th term
a1 = 4 * 1 + 16 = 4 + 16 = 20
2 th term
a2 = 4 * 2 + 16 = 8 + 16 = 24
3 th term
a3 = 4 * 3 + 16 = 12 + 16 = 28
4 th term
a4 = 4 * 4 + 16 = 16 + 16 = 32
etc.
Arithmetic sequence with first term
a1 = 20
and common difference d = 4
General formula for arithmetic sequence :
an = a1 + ( n  1 ) * d
In this case :
an = 20 + ( n  1 ) * 4 
Write the explicit formula for the geometric sequence.
a1 = 5 a2 = 20 a3 = 80