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

A rational expression is undefined when the value of its denominator is zero. Write and solve an expression where the denominator is zero. $x^2+1=0$ Use the addition property of equality to solve both equations for y. $x^2+1-1=0-1$ Simplify. $x^2=-1$ Since the square of a number can never be negative, this denominator can never be negative. This expression is defined for all real numbers.