If you are solving y 2+2y=48 by completing the square, the next line would be y 2 + 2y - 48 = 0
y 2 + 2y + 4 = 52
y 2 + 2y + 1 = 49

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?