Question

Write the explicit rule
50, 45, 40, 35, 30

Answer 1

an = -5n + 55.

Explanation:

This is arithmetic with common difference -5.

an = a1 + d(n-1)

an = 50 - 5(n - 1)

an = 50 - 5n + 5

an = -5n + 55.

Answer 2

a_n = 50 - 5n, for n = 1,2, 3, ...

Explanation:

a_1 = 50

a_2 = 50 - 5 = 45

a_3 = 50 - 2 * 5 = 40

a_n = 50 - (n - 1) * 5

a_n = 50 - 5n + 5

a_n = 50 - 5n