While we often input numbers into a function, we can also input expressions involving variables. We use the same technique as inputting numbers; we replace x with the new input. For the function = 1, we can input (x+1) for x, with the following result: + 1 = + 1 1 = + 2 + 1 1 = + 2 When we input (x+h), we arrive at + = + 1 = + 2 + 1 = + 2 + 1