Question

how many terms are there in the sequence of 1,5,7,11,.....77?​

Answer 1

Step-by-step explanation:

AP 1, 5,7,11,....,77

a=1 ,d=5-1=4, n=?, an=77

an =a +(n-1)d

77=1+(n-1)4

(n-1)=76/4

n-1=19

n=20

Answer 2

Answer:20

Step-by-step explanation:

a=1 , d=4 , l=77 , n=?

l = a +(n-1)d

77 = 1 +(n-1)4

76/4=n-1

n-1=19

n=20