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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 2.6.90

Finding Limits of Differences When x → ±∞


Find the limits in Exercises 84–90. (Hint: Try multiplying and dividing by the conjugate.)


lim x → ∞ (√(x² + x) − √(x² − x))

Guida verificata passo dopo passo
1
Identify the expression whose limit you need to find: \( \lim_{x \to \infty} (\sqrt{x^2 + x} - \sqrt{x^2 - x}) \).
To simplify the expression, multiply and divide by the conjugate: \( \frac{(\sqrt{x^2 + x} - \sqrt{x^2 - x})(\sqrt{x^2 + x} + \sqrt{x^2 - x})}{\sqrt{x^2 + x} + \sqrt{x^2 - x}} \).
The numerator becomes a difference of squares: \((x^2 + x) - (x^2 - x) = 2x\).
The expression simplifies to \( \frac{2x}{\sqrt{x^2 + x} + \sqrt{x^2 - x}} \).
Divide the numerator and the denominator by \(x\) to simplify further: \( \frac{2}{\sqrt{1 + \frac{1}{x}} + \sqrt{1 - \frac{1}{x}}} \), and evaluate the limit as \(x \to \infty\).

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