Find the limit $$\lim_{{x \to \infty}} \frac{3x^{-1} - 3x^{-3}}{4x^{-2} + x^{-5}},$$ we need to determine the behavior of the function as ( x ) approaches infinity

Muhammed_Burak_TÜRKY said

Answer:
To find the limit

\lim_{{x \to \infty}} \frac{3x^{-1} - 3x^{-3}}{4x^{-2} + x^{-5}},

we need to determine the behavior of the function as x approaches infinity.

  1. Rewrite the expression:

    • Rewrite x^{-n} as \frac{1}{x^n} .

      \frac{3x^{-1} - 3x^{-3}}{4x^{-2} + x^{-5}} = \frac{\frac{3}{x} - \frac{3}{x^3}}{\frac{4}{x^2} + \frac{1}{x^5}}
  2. Factor out the dominant term in both the numerator and denominator:

    • In the numerator, the dominant term as x \to \infty is \frac{3}{x} .

    • In the denominator, the dominant term as x \to \infty is \frac{4}{x^2} .

      Factor out \frac{1}{x} in the numerator and \frac{1}{x^2} in the denominator:

      \frac{\frac{3}{x} \left(1 - \frac{1}{x^2}\right)}{\frac{4}{x^2}\left(1 + \frac{1}{4x^3}\right)}
  3. Simplify the expression by canceling out common terms:

    • Simplify the expression:

      \frac{3x^{-1} \left(1 - x^{-2}\right)}{4x^{-2} (1 + x^{-3}/4)} = \frac{3}{4} x \left(1 - x^{-2}\right) \left(1 + x^{-3}/4\right)^{-1}

    As x \to \infty , terms with higher-degree negative exponents ( x^{-2}, x^{-3} ) will approach 0:

    \frac{3}{4} \left(1 - 0\right) \left(1 + 0\right)^{-1} = \frac{3}{4}

Therefore, the limit is:

\boxed{\frac{3}{4}}