Answer
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Work Step by Step
If the graph of a rational function $R(x)$ has the vertical asymptote $x=4$, this means that when $x\to4$, we have $R(x)\to -\infty\ or\ \infty$. And the condition that $R(x)\to -\infty\ or\ \infty$ is that the denominator approaches zero and the numerator approaches a nonzero constant, or in other words, $(x-4)$ must be present in the denominator.
