SOLUTION: when you simplify a rational expression, why are the numerator and the denominator factored? Why do you need a least common denominator when adding and subtracting rational express

Question 476470: when you simplify a rational expression, why are the numerator and the denominator factored? Why do you need a least common denominator when adding and subtracting rational expressions?
Answer by richard1234(7193) (Show Source): You can put this solution on YOUR website!
First of all, you do not need the LCD when adding and subtracting; you only need any common denominator (LCD is preferred, though). But you do need a common denominator; adding something like 1/4 + 3/2 does not make sense otherwise. And factoring rational expressions makes it more likely for certain factors to cancel out.
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