Question

Consider the arithmetic sequence 5 , 9 , 13 , . . .

a) What is its common difference ?

b) What is its 20th term ?​

Answer 1

Step-by-step explanation:

Common difference=9-5=4

20th term=a+19d

=5+19×4

=5+76

=81

Answer 2

Answer:

a) 4    

b) 81

Step-by-step explanation:

Common difference= a2-a1=9-5=4   or  Common difference = a3-a2 = 13-9 =4

An=A1 - (n-1)d

where d=common difference

A1 = first term = 5

n= number of term

in our case n = 20

A20= 5 + (20-1)4

      =5 + 19*4 = 5 + 76 = 81