Chapter 7 - Section 7.4 - Adding, Subtracting, and Multiplying Radical Expressions - Exercise Set - Page 439: 82

$\dfrac{2-4rs^2}{s}$

Factoring the expressions and then cancelling the common factors between the numerator and the denominator result to \begin{array}{l} \dfrac{14r-28r^2s^2}{7rs} \\\\= \dfrac{7r(2-4rs^2)}{7r\cdot s} &\text{...cancel $7r$} \\\\= \dfrac{2-4rs^2}{s} .\end{array}