OpenStudy (anonymous):

Ethan uses the function f(x) = 2x2 + 2x + 4 to track the temperature of a substance over 8 hours. You know that f(3) = 28 meaning that the temperature of the substance is 28°C when you plug in a 3 for x. What is the domain of Ethan’s function?

OpenStudy (anonymous):

The domain focuses on whether there is any restriction for the x-values. Usually restrictions apply when the x-values are on a fraction or under a square root sign, etc. In this example, it is just a quadratic. If you put infinty as x or -infinity as x, you will get a value of f(x). Therefore no matter what you put for x you would get a value. That means the domain for x is all real x.