Question

Write an explicit formula for an, the nth term
of the sequence 11, 2, -7

Answer 1

aₙ = 11 - 9(n - 1)

Explanation:

2 - 11 = (-7) - 2 = -9

So it is an arithmetic sequence

a₁ = 11

a₂ = 2 = 11 + (-9) = 11 + (2 - 1)*(-9)

a₃ = -7 = 2 + (-9) = 11 + (-9) + (-9) = 11 + (3 - 1)*(-9)

.....

aₙ = 11 + (n - 1) * (-9)

or

aₙ = 11 - 9(n - 1)

Answer 2

b(n) = 15 - 7(n - 1)

Explanation: