Chapter 9 - Quadratic Functions and Equations - 9-4 Factoring to Solve Quadratic Equations - Standardized Test Prep - Page 559: 50

2.5 inches

$x*(2x+1)=15$ $2x^2+x=15$ $2x^2+x-15=15-15$ $2x^2+x-15=0$ $2x^2+6x-5x-15=0$ $2x(x+3)-5(x+3)=0$ $(2x-5)(x+3)=0$ $2x-5=0$ $2x-5+5=0+5$ $2x = 5$ $2x/2 =5/2$ $x = 2.5$ $x+3=0$ $x+3-3=0-3$ $x = -3$ (we can't have a negative length, so this answer is invalid)