Answer
$\dfrac{9}{4(x-1)}$
Work Step by Step
$\dfrac{9}{x^2-1}\div\dfrac{12}{3x+3}$ is a rational expression
$\dfrac{9}{x^2-1}\div\dfrac{12}{3x+3} = \dfrac{\dfrac{9}{x^2-1}}{\dfrac{12}{3x+3}} = \dfrac{9(3x+3)}{12(x^2-1)} =\dfrac{9(3)(x+1)}{12(x^2-1)} = \dfrac{9(3)(x+1)}{12(x^2-1)} = \dfrac{9(3)(x+1)}{4(3)(x-1)(x+1)} = \dfrac{9}{4(x-1)}$
