So I'm having a bit of trouble here...
I want to prove the product rule:
So assuming that f and g are differentiable at Xo:
And in the same way, with some rearrangement.
Substituting equations 1 and 2 and multiplying out yields:
So now the example I'm following just leaves things here, so apparently this is enough, but I don't see how this simplifies to what I understand to be the goal of the exercise i.e.
Thanks in advance.