The First Fundamental Theorem of Calculus can be thought of as a short-cut formula for finding the derivative of accumulation functions.
Pick a function f(x) and a number a, and find the derivative of the accumulation function
∫ a to x f(x) dx.
If a different number is picked for a, does that change the derivative of the accumulation?
Why/why not? What changes if the upper limit of integration is x^2 instead of x?