## Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

$-1$
Using the product of the sum and difference of like terms which is given by $(a+b)(a-b)=a^2-b^2,$ the given expression is equivalent to \begin{array}{l}\require{cancel} (3+\sqrt{10})(3-\sqrt{10}) \\\\= (3)^2-(\sqrt{10})^2 \\\\= 9-10 \\\\= -1 .\end{array}