Question

What is the first term of an arithmetic sequence if the 29th term is 57 and the fifth term is 9?. ​

Answer 1

Answer:

a=1

d=2

Step-by-step explanation:

$a_{29}$=57

⇒a+28d=57             ----------(1)

$a_{5}$=9

⇒a+4d=9                 ----------(2)

Subtract (2) from (1):

a+28d-(a+4d) = 57-9

a+28d-a-4d = 48

24d=48

d=2                        -----------(3)

Substitute (3) in (2):

a+4d=9

a+4(2)=9

a=9-8

a=1