Adding and Subtracting Rational Expressions with Common Denominators
You must have a common denominator to add or subtract.
Simplify or factor the denominators first.
Create one fraction by add or subtracting the numerators. If you are subtracting, make sure to change the sign(s) of the term(s) in the second numerator.
Combine like terms in the numerator. Simplify or factor the numerator if at all possible.
Cancel out any common factor between the numerator and denominator.
Find the undefined terms. Set the original denominator equal to zero to find these values.
Least Common Multiple (LCM)
Adding and Subtracting Rational Expressions with Uncommon Denominators
Simplify or factor the denominators first.
Determine the Least Common Multiple (LCM) for the denominators.
Create common denominators by multiplying one or both of the fractions by a needed factor.
Create one fraction by add or subtracting the numerators. If you are subtracting, make sure to change the sign(s) of the term(s) in the second numerator.
Combine like terms in the numerator. Simplify or factor the numerator if at all possible.
Cancel out any common factor between the numerator and denominator.
Find the undefined terms. Set the original denominator equal to zero to find these values.