Question

Find a20, the 20th term, of the arithmetic sequence 1, 3, 5, 7, 9, …

Answer 1

The answer is 39.

Explanation:

The first term of arithmetic sequence is 1:

`a_(1)=1`

and the formula of arithmetic sequence is:

`a_(n)=2*n-1`

20th term of the arithmetic sequence will be:

`a_(20)=2*20-1=39`

Answer 2

a=1
common difference d=3-1=2
nth term= a+(n-1)d
2oth term= 1+(20-1)2
=1+38
=39