Derivative Function and Instantaneous Velocity

Find a polynomial function such as: 2 f(x) = 10 + 5x − x . Don’t use this one, but find one in a text, online, or create your own. First, calculate the derivative using the formal definition. Next, calculate the derivative using one of the appropriate derivative rules. Which way is obviously easier, and how you would prefer to find the derivative? Explain why calculus techniques are an improvement over using only algebra.