I am stuck on this one problem that I have for homework. The question says to find the critical numbers for f(x)= |3x-4|. I do not know how to take the derivative of an absolute value function. Any help would be greatly appreciated!!! Thank you in advance.
Well, I should think you would have to divide the derivative into different functions derived directly from d(3x-4)/dx, y' being multiplied by negative one for domains where y < 0, remaining the same where y > 0, and being nonexistent whenever y = 0.
 Actually, I think d|u|/dx still exists at u = 0 so long as du/dx = 0. (that is, if the function has a local min or max at an x-intercept)