# Week 15 : Adding and Subtracting Rational Expressions with Monomial Denominators

The strategies for adding and subtracting rational numbers can be used to add and subtarct rational expressions : write the expressions with common denominator.

For the example :

$\frac {2x}{7}\div\frac{5}{3x}$

So the non-permissible value is x = 0

A common denominator is $21x$

$\frac {2x}{7}\div\frac{5}{3x}$

= $\frac {6x^2+35}{21x}$