$\lim\limits_{h\to 0}\frac{(x+h)^3-x^3}{h}$
I tried to factor the top using the difference of cubes formula I looked up online, that gave an incorrect answer. I also tried to use a conjugate making $(x+h)^3=a$ and then I plugged in x and h afterwards, that did not work at all but I did get an answer, just not the right one. I can easily factor out an h and cancel it out but it isn't the right answer.