$P(x) = \dfrac{x-5}{(x^2-7x+12)}$ <br><br> For what value of $x$ is the function undefined ?

Question

$\begin{array}{1 1} (a)\; \text{x = 4 or x = 3} \\ (b)\; \text{x = -4 or x = 3} \\ (c)\; \text{x = 4 or x = -3} \\ (d)\; \text{x = -4 or x = -3} \end{array}$