To find the LCD of two rational expressions, we factor the expressions and multiply all of the distinct factors. For instance, if the factored denominators were (x+3)(x+4) ( x + 3 ) ( x + 4 ) and (x+4)(x+5) ( x + 4 ) ( x + 5 ) , then the LCD would be (x+3)(x+4)(x+5) ( x + 3 ) ( x + 4 ) ( x + 5 ) .
