Let $f(x)=\{\begin{array}{lll}{2}^{\frac{\sin <!--\; \; -->(x-<!--\; -\; -->3)}{x-<!--\; -\; -->[x]}}& ;& x<3\\ \frac{a|-<!--\; -\; -->x^2-<!--\; -\; -->12+7|}{b(x^2+12x-<!--\; -\; -->7)}& ;& x>3\\ b& ;& x=3\end{array}$ is continuous at x = 3, then (a, b) is