Product rule, Leibniz’s law
Derivative of a product:
Product rule, Leibniz’s law
You get the same result as developping first.
Very useful.
Derivative of a product
Proof
There has been a very important point in this operation.
That means that when h → 0 , it is not the value on the x-axis ,
(x + h) becomes ( x + 0 ),
but the value on the y-axis, f(x+h) becomes f(x) + 0