The sum of 2 times a number and 4 equals 5

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?

How many solutions does the nonlinear system of equations graphed below have? a. one b. zero c. four d. two

Factor the polynomial expression x6 – x3 – 20