A rational expression is a fraction of two polynomials. If you need to add or subtract two rational expressions, how would you do it? Describe, in your own words, the process for finding the Least Common Denominator (LCD) of two rational expressions. How is factoring related to this process in 4x/x^2 +6xy-7y^2 - 2x/x^2 +4xy-5y^2 of adding two rational expressions with different denominators.