Question

Find the 77th term for each sequence(use the equation: an=a1+(n-1)d)

A)5,10,15,20,25...
B)17,14,11,8,5

Answer 1

Explanation:

`an = a1 + (n - 1)d \\ d = a2 - a1 \\ a1 = 5 \\ a2 = 10 \\ d = 5 \\ an = 5 + (n - 1)5 \\ an = 5n \\ a77 = 5 * 77 = 385`

For B

`a1 = 17 \\ a2 = 14 \\ d = 14 - 17 = - 3 \\ an = 17 + (n - 1) * - 3 \\ an = 17 - 3n + 3 \\ an = 20 - 3n \\ a77 = 20 - 3 * 77 \\ a77 = - 211`