If a1 is the first term of an arithmetic sequence and d is the common difference, then the formula for finding thenthtermofthesequenceisan =a1+(n−1)d.
Wehavebeengivena1 =5andd=15. We’reaskedtofindn=40.
an =a1 +(n−1)d a40 = 5+(40−1)·15
= 5+39·15 = 590
The 40th term of this sequence is 590.