Leibnitz Integral [rule]
Permanently Deleted
For number 4 (or maybe a new number), if a(x) and b(x) are constant, the derivatives d/dx a(x) and d/dx b(x) are zero, so all that is left is that d/dx becomes a partial derivative and can move inside the integral.
As a German, whenever I hear that term I think of this
Leibnitz nuts