An arithmetic sequence is represented by the explicit formula a(n) = 2 + 9(n - 1). what is the recursive formula? . a. a(n) = a(n - 1) + 2. b. a(n) = a(n - 1) + 9. c. a(n) = a(n - 1) - 9. d. a(n) = a(n - 1) - 3

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?