Let $$ f(x) = \begin{cases} \frac{sin|x^2 - 5x + 6|}{x^2 - 5x + 6}, & \text{if x $\ne$ 2,3} \\ 1, & \text{if x = 2 or 3} \end{cases}$$
I want to find all the points where f is differentiable. Clearly, I need to check only at the points 2 and 3. I tried differentiating the first part, but couldn't solve.
Please Help.