Finding Horizontal And Vertical Asymptotes Of Rational Functions

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For horizontal asymptotes in rational functions, the value of \(x\) in a function is either very large or very small; this means that the terms with largest exponent in the numerator and denominator are the ones that matter. For example, with \( f(x) = \frac{3x^2 + 2x - 1}{4x^2 + 3x - 2} ,\) we only need to consider \( \frac{3x^2}{4x^2} .\) Since the \( x^2 \) terms now can cancel, we are left with \( \frac{3}{4} ,\) which is in fact where the horizontal asymptote of the rational function is.

In a case like \( \frac{3x}{4x^3} = \frac{3}{4x^2} \) where there is only an \(x\) term left in the denominator after the reduction process above, the horizontal asymptote is at 0.

In a case like \( \frac{4x^3}{3x} = \frac{4x^2}{3} \) where there is only an \(x\) term left in the numerator after the reduction process above, there is no horizontal asymptote at all. (There may be an oblique or "slant" asymptote or something related.)

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