#### Answer

Fill the blanks with:
complex, complex

#### Work Step by Step

Complex rational expressions, or complex fractions
have numerators and/or denominators containing rational expressions.
For example, $\displaystyle \quad\frac{1+\frac{1}{x}}{\frac{x-1}{x+1}},\qquad \frac{\frac{a}{2}-\frac{3+a}{b}}{\frac{a+1}{b}}$
(These are first mentioned just before example 9)