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Ch. 2 - Limits and Continuity
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Non è quello che usi tu?Cambia libro di testo
Capitolo 2, Problema 2.6.47

Infinite Limits


Find the limits in Exercises 37–48. Write ∞ or −∞ where appropriate.


lim x→0 4 / x²/⁵

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First, identify the form of the limit as x approaches 0. The expression given is \( \frac{4}{x^{2/5}} \).
Recognize that as x approaches 0, \( x^{2/5} \) also approaches 0. Since \( x^{2/5} \) is in the denominator, the expression \( \frac{4}{x^{2/5}} \) will tend towards infinity.
Consider the direction from which x approaches 0. If x approaches 0 from the positive side (x → 0⁺), \( x^{2/5} \) is positive, and thus \( \frac{4}{x^{2/5}} \) approaches positive infinity.
If x approaches 0 from the negative side (x → 0⁻), \( x^{2/5} \) is still positive because the fifth root of a negative number is negative, but squaring it makes it positive. Therefore, \( \frac{4}{x^{2/5}} \) also approaches positive infinity.
Conclude that the limit of \( \frac{4}{x^{2/5}} \) as x approaches 0 is positive infinity, regardless of the direction from which x approaches 0.

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Infinite Limits

Infinite limits occur when the value of a function increases or decreases without bound as the input approaches a certain point. In this context, as x approaches 0, the function 4/x²/⁵ may tend towards infinity or negative infinity, depending on the behavior of the denominator, which becomes very small, causing the overall expression to grow very large.
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Behavior of Rational Functions

Rational functions are expressions involving ratios of polynomials. The behavior of these functions near points where the denominator approaches zero is crucial for determining limits. As x approaches 0 in 4/x²/⁵, the denominator x²/⁵ approaches zero, leading to a potential infinite limit, as the numerator remains constant and the denominator shrinks.
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Power Functions and Exponents

Understanding power functions and their exponents is essential for analyzing limits involving expressions like x²/⁵. The exponent determines how rapidly the function approaches zero or infinity as x approaches a specific value. In this case, x²/⁵ indicates a root, which affects the rate at which the denominator approaches zero, influencing the limit's behavior.
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