I could bark out the boilerplate response for low-effort copypasted homework questions, but I'm out of breath today. Let's settle for a compromise. Here's a conceptual example that is intentionally not exactly what you need, but can be rearranged with some minor effort.
f = @(x) (x.^2 + 2*x +2) ./ (exp(x) + x.^(1/2) .* cos(x));
This example defines an anonymous function, which should be sufficient for the task, but there are other ways to define a function. Refer to the docs: