` a) ` ` \frac{12x}{x^2 - 9} + \frac{2x}{x + 3} `
` = \frac{12x + 2x(x - 3)}{(x - 3)(x + 3)} `
` = \frac{12x + 2x^2 - 6x}{(x - 3)(x + 3)} `
` = \frac{2x^2 - 6x}{(x - 3)(x + 3)} `
` = \frac{2x(x - 3)}{(x - 3)(x + 3)} `
` = \frac{2x}{x + 3} `
` b) ` ` \frac{1 - x}{x - 3} + \frac{x - 2}{x - 3} `
` = \frac{1 - x + x - 2}{x - 3} `
` = \frac{-1}{x - 3} `