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# 2015 AP Calculus 2c

Rate of change of difference between functions.

## Want to join the conversation?

• should it be the absolute value, because the vertical distance can't be negative?
• Just by eyeballing it, we know f(x) - g(x) can't be negative because we're looking at region S, where f(x) > g(x)! So an absolute value function would be redundant.

If you're referring to the derivative, remember it can be negative because we're not talking about distances; we're talking about rates, and rates can be positive (increasing) or negative (decreasing).
• At , how do I know it is h'(1.8)? It makes sense when Sal says it, but on a real AP test, how do I interpret the written question correctly to assume they are asking for the derivative (h'(x))?
Hope this question makes sense, and thanks so much in advance!