Sometimes we need to find partial derivatives for functions with three or more variables, and we’ll do it the same way we found partial derivatives for functions in two variables. We’ll take the derivative of the function with respect to each variable separately, which means we’ll end up with one partial derivative for each of our variables. When we take the derivative with respect to one variable, we’ll treat all the other variables as constants.
Read MoreWe already learned in single-variable calculus how to find second derivatives; we just took the derivative of the derivative. Remember how we even used the second derivative to help us with inflection points and concavity when we were learning optimization and sketching graphs?
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