For which of the following values of $x$ is the rational expression undefined?
$\frac{x+1}{x^2-9}$

• A. $0$
• B. $\(\pm\)3$
• C. $\(\pm\)9$
• D. $\(\pm\)1$

Answer: (B)

Verified step by step guidance

1. Identify when a rational expression is undefined: it is undefined when its denominator is equal to zero.
2. Set the denominator equal to zero: \(x^2 - 9 = 0\).
3. Recognize that \(x^2 - 9\) is a difference of squares, which factors as \((x - 3)(x + 3)\).
4. Set each factor equal to zero to find the values of \(x\) that make the denominator zero: \(x - 3 = 0\) and \(x + 3 = 0\).
5. Solve each equation to find \(x = 3\) and \(x = -3\), which are the values for which the rational expression is undefined.