### Home > CCA2 > Chapter Ch10 > Lesson 10.1.1 > Problem10-9

10-9.

Write a formula for the $n$th term of each of the following series.

1. $3+10+17+$

The terms are increasing by $7$ each time.

$t(1)=3$

$t(n)=3+7(n-1)$

Simplified, this becomes $t(n)=7n-4$.

1. $20+11+2+$

What is added to each term to get the next?

What is the first term?