PLEASE SOMEBODY SMART HELP

Identify a1 and r for the geometric sequence an= -256(-1/4) n-1

If f(x)=x+7 and g(x)=1/x what is (fog)(x)

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?