Math Problem Statement

Evaluate the limit: lim (x -> infinity) [(2x√x - x + 3) / (3 / x^(1/2))]

Solution

The given limit is:

limx2xxx+33x12\lim_{x \to \infty} \frac{2x\sqrt{x} - x + 3}{\frac{3}{x^{\frac{1}{2}}}}

To evaluate this limit, let's break it down step by step:

Step 1: Simplify the denominator

The denominator is 3x12=3x12\frac{3}{x^{\frac{1}{2}}} = 3x^{-\frac{1}{2}}. So, the expression becomes:

2xxx+33x12\frac{2x\sqrt{x} - x + 3}{3x^{-\frac{1}{2}}}

Step 2: Multiply numerator and denominator by x12x^{\frac{1}{2}}

We multiply both the numerator and the denominator by x12x^{\frac{1}{2}} to eliminate the negative exponent in the denominator:

x12(2xxx+3)3\frac{x^{\frac{1}{2}}(2x\sqrt{x} - x + 3)}{3}

Simplifying the terms in the numerator:

  • x122xx=2x32x12=2x2x^{\frac{1}{2}} \cdot 2x\sqrt{x} = 2x^{\frac{3}{2}} \cdot x^{\frac{1}{2}} = 2x^2
  • x12(x)=x32x^{\frac{1}{2}} \cdot (-x) = -x^{\frac{3}{2}}
  • x123=3x12x^{\frac{1}{2}} \cdot 3 = 3x^{\frac{1}{2}}

So the expression becomes:

2x2x32+3x123\frac{2x^2 - x^{\frac{3}{2}} + 3x^{\frac{1}{2}}}{3}

Step 3: Analyze the limit as xx \to \infty

As xx approaches infinity, we observe the terms in the numerator:

  • The term 2x22x^2 dominates because it has the highest power of xx.
  • The other terms (x32-x^{\frac{3}{2}} and 3x123x^{\frac{1}{2}}) become negligible as xx \to \infty.

Thus, the expression approaches:

limx2x23=\lim_{x \to \infty} \frac{2x^2}{3} = \infty

Conclusion:

The limit is infinite.

\boxed{\infty}

Would you like further clarification on any step, or to explore related problems?

Here are 5 related questions:

  1. What happens if the power of xx in the denominator is higher than in the numerator?
  2. How do limits behave when approaching 00 instead of infinity?
  3. Can L'Hopital's rule be used here? Why or why not?
  4. How does multiplying by x12x^{\frac{1}{2}} help simplify the problem?
  5. What techniques can be applied to solve indeterminate limits?

Tip: When evaluating limits at infinity, always focus on the highest power terms in both the numerator and denominator to simplify the expression.

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Math Problem Analysis

Mathematical Concepts

Limits
Asymptotic behavior
Simplification of expressions

Formulas

lim (x -> infinity) [(2x√x - x + 3) / (3 / x^(1/2))]
Multiplication by x^(1/2) to eliminate negative exponents

Theorems

Limit properties
Asymptotic dominance of higher-degree terms

Suitable Grade Level

Grades 11-12, Undergraduate Calculus