Math Problem Statement

656. Пусть x → + ∞. Выделить главный член вида Cx^n и определить порядки роста относительно бесконечно большого x следующих функций: a) x^2 + 100x + 10000; b) \frac{2x^5}{x^3 - 3x + 1}; в) \sqrt[3]{x^2 - x + \sqrt{x}}; г) \sqrt{1 + \sqrt{1 + \sqrt{x}}}.

Solution

The task in the image asks to find the leading term of each function as x+x \to +\infty and determine the growth order of these functions. Let's go through each one step by step.

Given functions:

  1. a) x2+100x+10000a) \ x^2 + 100x + 10000
  2. b) 2x5x33x+1b) \ \frac{2x^5}{x^3 - 3x + 1}
  3. c) x2x+x3c) \ \sqrt[3]{x^2 - x + \sqrt{x}}
  4. d) 1+1+xd) \ \sqrt{1 + \sqrt{1 + \sqrt{x}}}

Analyzing each function as x+x \to +\infty:


1. a) x2+100x+10000a) \ x^2 + 100x + 10000

For large xx, the highest degree term dominates. In this case, x2x^2 grows faster than 100x100x and 1000010000.

  • Leading term: x2x^2
  • Growth order: x2x^2

2. b) 2x5x33x+1b) \ \frac{2x^5}{x^3 - 3x + 1}

For large xx, the dominant term in the numerator is 2x52x^5, and the dominant term in the denominator is x3x^3.

  • Simplifying for large xx: 2x5x33x+12x5x3=2x2\frac{2x^5}{x^3 - 3x + 1} \approx \frac{2x^5}{x^3} = 2x^2
  • Leading term: 2x22x^2
  • Growth order: x2x^2

3. c) x2x+x3c) \ \sqrt[3]{x^2 - x + \sqrt{x}}

For large xx, the highest degree term inside the cube root is x2x^2.

  • Approximating for large xx: [ \sqrt[3]{x^2 - x + \sqrt{x}} \approx \sqrt[3]{x^2} ] x23=x2/3\sqrt[3]{x^2} = x^{2/3}
  • Leading term: x2/3x^{2/3}
  • Growth order: x2/3x^{2/3}

4. d) 1+1+xd) \ \sqrt{1 + \sqrt{1 + \sqrt{x}}}

For large xx, the dominant term inside the square roots will be the innermost square root x\sqrt{x}.

  • Approximating for large xx: 1+1+x1+xx=x1/4\sqrt{1 + \sqrt{1 + \sqrt{x}}} \approx \sqrt{1 + \sqrt{\sqrt{x}}} \approx \sqrt{\sqrt{x}} = x^{1/4}
  • Leading term: x1/4x^{1/4}
  • Growth order: x1/4x^{1/4}

Summary of Leading Terms and Growth Orders:

  • (a): Leading term: x2x^2, Growth order: x2x^2
  • (b): Leading term: 2x22x^2, Growth order: x2x^2
  • (c): Leading term: x2/3x^{2/3}, Growth order: x2/3x^{2/3}
  • (d): Leading term: x1/4x^{1/4}, Growth order: x1/4x^{1/4}

Let me know if you'd like more details on any of these steps or have any questions!

Relative questions:

  1. How does the growth order of a polynomial compare to an exponential function?
  2. What happens if we compare functions with logarithmic growth versus polynomial growth?
  3. How can L'Hopital's rule help in analyzing limits involving infinity?
  4. What are the properties of cube roots and square roots in limit calculations?
  5. How would the growth change if we had additional terms involving ln(x)\ln(x) in these functions?

Tip:

When analyzing functions as xx \to \infty, always focus on the highest-degree terms because they dominate the behavior of the function in this limit.

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Math Problem Analysis

Mathematical Concepts

Asymptotic Analysis
Limits
Polynomials
Rational Functions
Radical Expressions

Formulas

Leading term of polynomials: highest degree term dominates
For rational functions: highest degree term in numerator and denominator dominates
Cube root: \sqrt[3]{x^n} = x^{n/3}
Square root: \sqrt{x^n} = x^{n/2}

Theorems

Growth Order Theorem

Suitable Grade Level

University Level (Mathematics, Analysis)