Chapter R - Elementary Algebra Review - R.1 Introduction to Algebraic Expressions - R.1 Exercise Set - Page 938: 22

$-1$

Using multiplication, the given expression, $ \left( -\dfrac{4}{7} \right)\left( \dfrac{7}{4} \right) ,$ evaluates to \begin{array}{l}\require{cancel} \left( -\dfrac{\cancel{4}}{\cancel{7}} \right)\left( \dfrac{\cancel{7}}{\cancel{4}} \right) \\\\= -1.\end{array}