## Introductory Algebra for College Students (7th Edition)

$x=4$ or $x=5$
A rational expression is undefined when the value of its denominator is zero. Write and solve an expression where the denominator is zero. $x^2-9x+20=0$ A product is zero when either factor is zero. Factor the trinomial. $(x-4)(x-5)$ Solve each factor for zero. $x-4=0$ or $x-5=0$ Use the addition property of equality to solve both equations for x. $x-4+4=0+4$ or $x-5+5=0+5$ Simplify. $x=4$ or $x=5$