Chapter 4 - Polynomials - Test: Chapter 4 - Page 300: 31

$25t^2-49$

Using $(a+b)(a-b)=a^2-b^2$ or the product of the sum and difference of like terms, the product of the given expression, $ (5t-7)(5t+7) ,$ is \begin{array}{l}\require{cancel} (5t)^2-(7)^2 \\\\= 25t^2-49 .\end{array}