Sorry for not showing my work on my last post, I'm on my good for nothing blackberry and apparently cannot type. My question was: Use first principles definition to find dy/dx: y=(-4/3x) lim x--> 0 --------- (X,-4/3x) (X+h, -4/3(X+h) =lim»0 ((-4/3(x+h))-(-4/3x))/x+h-x I have gotten the answer 4/3x^2 through my proof, but I knew what the answer was (I looked at the back in frustration). I'm afraid I may have broken a few rules when I found a common denominator for the numerator ( (3)(x+h)(3x)) and worked it down to =lim»0 -12x+12x+12h/[3x+3h](3x) =lim »0 4h/3x^2h+3hx Any help is appreciated !!!!