Chapter 9 - Quadratic Functions and Equations - 9-4 Factoring to Solve Quadratic Equations - Practice and Problem-Solving Exercises - Page 559: 42

a) $x^2-3x-40=0$ b) $x^2-x-6 = 0$ c) $x^2+9.5x-5=0$ d) $21x^2+x-10 =0$ answers may vary

a) $x=-5, 8$ $(x+5)(x-8)$ $x^2+5x-8x-40$ $x^2-3x-40$ b) $x=-2, 3$ $(x+2)(x-3)$ $x^2+2x-3x-6$ $x^2-x-6$ c) $x=1/2, -10$ $(x+10)(x-1/2)$ $x^2+10x-.5x-5$ $x^2+9.5x-5$ d) $x=2/3, -5/7$ $(x+5/7)(x-2/3)$ $(7x+5)(3x-2)$ $21x^2-14x+15x-10$ $21x^2+x-10$