Question

Bamboo plants grow rapidly. A bamboo plant is 130 inches tall. Tomorrow it will be 143 inches tall, the next day it will be 156 inches tall, and on the next day it will be 169 inches tall. What is an explicit formula to represent the height of the bamboo plant as an arithmetic sequence? How tall will the plant be in 13 days?

Answer 1

An arithmetic sequence has a common difference.
143 - 130 = 13
156 - 143 = 13
169 - 156 = 13
The common difference is 13.

a1 = 130
a2 = 130 + 13
a3 = 130 + 2 * 13
a4 = 130 + 3 * 13
...
an = 130 + (n - 1) * 13

an = 130 + 13(n - 1)

an = 130 + 13n - 13

an = 117 + 13n

an = 13n + 117