How do you write 4x4 in exponents?

There are really infinitely many ways to write 4x4 in exponents, but consider what 4x4 really means and what an exponent is. First, an exponent states how many times a number is multiplied by itself, such as 3^2, or 3 "squared", meaning that the result is 3x3. With this in mind, look back at 4x4. Since the number multiplied is the same, we can write it using exponents. In this case, we are going to have 4^2, or four "squared". This is of course only one example, but I'm sure that that will likely be sufficient for your purposes.