Chapter 4 - Polynomial and Rational Functions - 4.5 The Real Zeros of a Polynomial Function - 4.5 Assess Your Understanding - Page 235: 114

$-3$

Step 1. Given $x=-2$ as a zero, use synthetic division to find the quotient as $x^2+3x-1$, see figure. Step 2. Solve $x^2+3x-1=0$ to get $x=\frac{-3\pm\sqrt {9+4}}{2}=\frac{-3\pm\sqrt {13}}{2}$ Step 3. Thus, the sum of the remaining zeros is $-3$