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The function $f(x) = \dfrac{x^{2} - 1}{x - 1}$ is undefined at:

A$x = -1$
B$x = 1$
C$x = 0$
D$x = 2$
Answer & Solution
Correct answer: B. $x = 1$
The denominator $x - 1 = 0$ when $x = 1$. Division by zero is undefined, so $x = 1$ must be excluded from the domain (even though $x^{2} - 1 = (x-1)(x+1)$ allows the expression to be 'simplified' to $x + 1$ for $x \ne 1$).
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