Chapter 1 - Introduction to Algebraic Expressions - 1.8 Exponential Notation and Order of Operations - 1.8 Exercise Set - Page 67: 91

$-9x-1$

Since the grouping symbol is preceded by a negative sign, then the sign of each term inside the grouping symbol alters once the grouping symbol is removed. Hence, the given expression, $ -(9x+1) $, is equivalent to \begin{array}{l}\require{cancel} -9x-1 .\end{array}