Limits at Infinity, Part I — Question 4

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Question 4

Evaluate the limit: limx→−∞6x3+4x−1−2x3+7x2+5\lim_{x \to -\infty} \frac{6x^3 + 4x - 1}{-2x^3 + 7x^2 + 5}

Original worksheet page 1: question and worked solution for 2-7-004
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Question 4 - Solution

We are given: limx→−∞6x3+4x−1−2x3+7x2+5\lim_{x \to -\infty} \frac{6x^3 + 4x - 1}{-2x^3 + 7x^2 + 5}

We divide both the numerator and denominator by x3x^3, the highest power of xx:

=limx→−∞6+4x2−1x3−2+7x+5x3= \lim_{x \to -\infty} \frac{6 + \frac{4}{x^2} - \frac{1}{x^3}}{-2 + \frac{7}{x} + \frac{5}{x^3}}

As x→−∞x \to -\infty, all terms with negative exponents approach zero:

=6−2=−3= \frac{6}{-2} = -3

Final Answer: −3\boxed{-3}

Original worksheet page 2: question and worked solution for 2-7-004

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