Question

The start of a quadratic

sequence is
8, 18, 30, 44, 60, …
What is the nth term rule for this sequence?

Answer 1

You can find the general rule in two ways
8 = 1x8, 18 = 2x9, 30 = 3x10, 44 = 4x11, 60 = 5x12 … so in general T(n) = n(n + 7)

Or because the second differences are constant we know it uses squares
8 = 1^2 + 7, 18 = 2^2 + 14, 30 = 3^2 + 21, 44 = 4^2 + 28, 60 = 5^2 + 35 … so in general T(n) = n^2 + 7n

Answer 2

The correct option is D

98

The general term of the sequence is n(n+7)