Answer:
The 21st term is 137.
Step-by-step explanation:
Arithmetic progression:
In an arithmetic progression the difference between consecutive terms is always the same, and its called common difference.
The nth term is given by:
[tex]a_n = a_1 + (n-1)d[/tex]
In which [tex]a_1[/tex] is the first term and d is the common difference.
The first two terms are -3, 4.
This means that [tex]a_1 = -3, d = 4 - (-3) = 7[/tex]
So
[tex]a_n = a_1 + (n-1)d[/tex]
[tex]a_n = -3 + 7(n-1)[/tex]
The 21st term is
[tex]a_{21} = -3 + 7(21-1) = -3 + 140 = 137[/tex]
The 21st term is 137.
