Chapter 7 - Sections 7.1-7.5 - Integrated Review - Radicals and Rational Exponents - Page 447: 33

$4x^2-5$

Using $(a+b)(a-b)=a^2-b^2$ or the product of the sum and difference of like terms, the given expression, $ \left( 2x-\sqrt{5} \right)\left( 2x+\sqrt{5} \right) ,$ is equivalent to \begin{array}{l}\require{cancel} (2x)^2-(\sqrt{5})^2 \\\\= 4x^2-5 .\end{array}