Chapter 6 - Section 6.1 - The Greatest Common Factor - Exercise Set - Page 422: 86

$10,-1$

lets call the numbers $x, y$ $x+y = 9$ $x\times y = 20$ $x+y =9$ Therefore $x=9- y$ $x\times y =20$ Therefore $(9-y)\times y = 20$ $9y - y^2 = 20$ $ - y^2 + 9y - 20= 0$ $ - (y - 10) (y+1)$ $ y = 10, -1$ $x = -1, 10$ Therefore the numbers are $10,-1$