Online Calculus Problem Generator

Whenever I need to work on a problem, I have to start with something like<br>“Find what values of k and n satisfy the inequality” and then spend 10 minutes thinking up a simple expression, which can be annoying. So I propose a calculator that takes in parameters (like what type of problem, whether you have a specific variable you want, the difficulty level, etc.) and spits out a calculus problem with a randomly generated expression, like “Find the value of k such that the function f(x) = x^4 + 5x^2 + 2x + k has exactly 2 roots”. A feature to generate solutions would be nice too.