x^2 – x – 6 = (x – 3)(x + 2)

x^2 – 6x + 9 = (x – 3)^2

So the LCD will be (x + 2)(x – 3)^2. Let’s leave it factored for the moment, because it’s almost always easier to work with that.

To get the first fraction over the LCD, you’ll multiply by (x – 3)/(x – 3). That gives you

3x(x – 3)/LCD = (3x^2 – 9x)/LCD

To get the second over the LCD, you’ll multiply by (x + 2)/(x + 2). That gives you

(x + 2)(x + 2)/LCD = (x^2 + 4x + 4)/LCD

Putting them together, then, you have

(3x^2 – 9x + x^2 + 4x + 4)/LCD

= (4x^2 -5x + 4)/LCD

Your last step would be to factor the numerator and see if anything canceled with the denominator. If it doesn’t factor, then you’re done. I’ll leave that to you to determine.