Question

What is the general term equation, an, for the arithmetic sequence 5, 1, â3, â7, . . . , and what is the 21st term of this sequence?

Answer 1

hello :

the nth term ( general term  of an arithmetic sequence is :

An =A1+(n-1)d   ....a common difference is : d , A1 : the first terme
A1 = 5    and : d = 1 - 5 = - 4    n = 21
A21 = 5 + (21 -1)(-4)
A21 = 5 - 80 = -75