Which value is not in the domain of f(x) = 1/(x^2 - 5x + 6)?

Correct answer: x = 2

For a rational function, the domain contains all real inputs for which the denominator is non-zero. Factor the denominator: x² - 5x + 6 = (x - 2)(x - 3). It becomes zero when x = 2 or x = 3, so both values must be excluded from the domain. Among the four choices, only x = 2 is an excluded value; x = 0 gives denominator 6, x = 1 gives denominator 2, and x = 4 gives denominator 2, so each of those produces a defined function value. Therefore option A is the correct response. Although x = 3 is also outside the domain, it is not listed, so there is no ambiguity in the given options.