Section 1.6 : Rational Expressions
5. Perform the indicated operation in the following expression and reduce the answer to lowest terms.
\[\frac{{{x^2} - 49}}{{2{x^2} - 3x - 5}} \div \frac{{{x^2} - x - 42}}{{{x^2} + 7x + 6}}\]Show All Steps Hide All Steps
Start SolutionSo, we first need to do is convert this into a product.
\[\frac{{{x^2} - 49}}{{2{x^2} - 3x - 5}} \div \frac{{{x^2} - x - 42}}{{{x^2} + 7x + 6}} = \frac{{{x^2} - 49}}{{2{x^2} - 3x - 5}}\,\centerdot \,\frac{{{x^2} + 7x + 6}}{{{x^2} - x - 42}}\]Make sure that you don’t do the factoring and canceling until you’ve converted the division to a product.
Show Step 2Now we can factor each of the terms as much as possible to get,
\[\frac{{{x^2} - 49}}{{2{x^2} - 3x - 5}} \div \frac{{{x^2} - x - 42}}{{{x^2} + 7x + 6}} = \frac{{\left( {x - 7} \right)\left( {x + 7} \right)}}{{\left( {2x - 5} \right)\left( {x + 1} \right)}}\centerdot \frac{{\left( {x + 1} \right)\left( {x + 6} \right)}}{{\left( {x - 7} \right)\left( {x + 6} \right)}}\] Show Step 3Finally cancel as much as possible to reduce to lowest terms and do the product.
\[\frac{{{x^2} - 49}}{{2{x^2} - 3x - 5}} \div \frac{{{x^2} - x - 42}}{{{x^2} + 7x + 6}} = \require{bbox} \bbox[2pt,border:1px solid black]{{\frac{{x + 7}}{{2x - 5}}}}\]