That "6x" is wrong. You are using the chain rule but you need to multiply by the derivative of 6x, 6, not the 6x itself.
I have got a funny result for a problem:
given the function
by differentiating I got and the answer is considered a wrong one...
, but by calculating f(5) for what I obtained gave me a correct answer, is that a coincidence or I miss something?
although, the program we are entering our answers "asked" me imperatively to do a step further and factor x^2 under the radical; it considered this answer as not correct until I did the following:
IMO it's kind of useless... maybe there is a reason(I'm serious, actually - it's not sarcasm), from a deep mathematical point of view and me, as a novice, I am not aware of... what do you think?