So I tried solving this substituting x = 0 then I get f'(x) = 0.
But that seems to be wrong.
If I use the product law of derivatives then I get 0*(0-1)*(0-2)....=0
Why we can't substitute x=0 first, then take the derivative of the entire expression, instead we have to first take the derivative then substitute x=0 which gives another answer...
How to calculate this properly?