hey guys, whats up. Its my first time posting so yeah.... Ok i'm attempting to do the following problem... let f(x) = x^3 for x is less than or eqaul to 4. (6x^2)-8x when x is greater than 4 i need to see if f(x) is differentiable at x = 4. I tried it through the definition of the derivative as a function. For the first part im using x^3 and plugging it into f(x) in the def. of the deriv. and i cant seem to figure out what to do with the h I have in the exponent and in the denomenator. i fot as far as.... x^3 lim (a^h-1)/h....I know what x is, 4...but what do i do with the a and the h? please someone help, thanks.