The order pairs (1, 2), (2, 5), (3, 10), (4, 17), and (5, 26) represent a function. what is a rule that could represent this function

You are standing next to a really big circular lake. you want to measure the diameter of the lake, but you don't want to have to swim across with a measuring tape! you decide to walk around the perimeter of the lake and measure its circumference, and find that it's 400\pi\text{ m}400? m. what is the diameter dd of the lake?