Use the alternative formula for the derivative to find the derivative of F of X equal three X / X - 1. So the first thing we need to realize is the alternative definition as the limit as Z approaches X of F of Z -, F of X / Z -, X. So the limit as Z approaches X of three Z / Z - 1 minus three X / X - 1 all over Z -, X getting a common denominator three Z * X - 1 - 3 X times Z - 1 all over Z - 1 * X - 1, and that whole thing over Z -, X. Now when we have that over Z -, X, we can really think of moving that Z -, X into the denominator portion. So if we distribute out, we get three ZX -3 Z -3 ZX plus 3X all over the denominator. The three ZX and the -3 ZX are going to cancel. So we have -3 Z plus 3X over Z -, 1 X -1 Z minus X. When I pull out a -3, we get Z -, X and the Z -, X on top and bottom Cancel so -3 / Z - 1 * X - 1. Now, the fact that we have Z approaching X means we're going to put X in every time we see the Z so -3 / X - 1 * X - 1 or -3 / X - 1 ^2.