In this video, we learn how to subtract rational expressions. To start, you will need to find common denominators. To do this, factor out the denominators in the fractions on both sides of the equations. Now you need to build the lowest common denominator for these two fractions. To do this, take the first denominator and take whatever is missing from the second. After you do the math for this, you will build new fractions with the common denominator as the denominator. Leave the denominator in factored form. When you find the answer, make sure it's in simplest form and you're done!