Chapter 4 Quadratic Functions and Factoring - 4.8 Use the Quadratic Formula and the Discriminant - 4.8 Exercises - Skill Practice - Page 296: 26

$$r=8,\:r=1$$

Solving the equation using the quadratic formula, we find: $$r_{1,\:2}=\frac{-\left(-9\right)\pm \sqrt{\left(-9\right)^2-4\cdot \:1\cdot \:8}}{2\cdot \:1} \\ r=8,\:r=1$$ Checking by factoring the expression, we find: $$r\left(r-1\right)-8\left(r-1\right)\\ \left(r-1\right)\left(r-8\right)$$