What is the domain of the function f of x is equal to the fraction with numerator x plus 1 and denominator x squared minus 6 x plus 8 ?

A rational function is undefined wherever its denominator equals zero. Factor the denominator: x² − 6x + 8 = (x − 2)(x − 4), so it is zero at x = 2 and x = 4. The domain is all real numbers except 2 and 4, which is choice C.

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