Chapter 5 - Exponents and Polynomials - 5.1 - Addition and Subtraction of Polynomials - Problem Set 5.1 - Page 195: 55

$-x^2-13x-12$

By using the distributive property, removing the grouping symbols, and then combining like terms, the given expression, $ (x^2-7x-4)+(2x^2-8x-9)-(4x^2-2x-1) ,$ simplifies to \begin{array}{l}\require{cancel} x^2-7x-4+2x^2-8x-9-4x^2+2x+1 \\\\= (x^2+2x^2-4x^2)+(-7x-8x+2x)+(-4-9+1) \\\\= -x^2-13x-12 .\end{array}