Chapter 1 - Introduction to Algebraic Expressions - 1.7 Multiplication and Division of Real Numbers - 1.7 Exercise Set - Page 58: 96

$-\dfrac{10}{17}$

To get the reciprocal of a number, interchange the numerator and the denominator. Hence, the reciprocal of the given expression, $ -1.7 $, is \begin{array}{l} -\dfrac{17}{10} \\\\= -\dfrac{10}{17} .\end{array}