# Chapter 5 - Polynomials and Factoring - 5.1 Introduction to Factoring - 5.1 Exercise Set - Page 310: 51

$(7x+5)(x^2-3)$

#### Work Step by Step

Using factoring by grouping, the factored form of the given expression, $7x^3+5x^2-21x-15 ,$ is \begin{array}{l} (7x^3+5x^2)-(21x+15) \\\\= x^2(7x+5)-3(7x+5) \\\\= (7x+5)(x^2-3) .\end{array}

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