ACT Math · Polynomial and rational functions
For the function f(x) = (x²-16)/(x-4), what is the value that f(x) approaches as x approaches 4, even though f(4) is undefined?
For the function , what is the value that approaches as approaches 4, even though is undefined?
Answer and explanation
Answer: C: 8
Factor the numerator: for . The function has a hole at , and the value it approaches is , choice C. Choice A () is the numerator's value at with no regard for the zero in the denominator. Choice B () is the -value of the hole, not the height. Choice D () is the constant in the numerator. Because the factor cancels, there is no vertical asymptote here.
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