Math Problem Statement

Find the limit of (x*y^4) / (x^4 + y^4) as (x, y) approaches (0, 0).

Solution

The limit problem in the image is as follows:

lim(x,y)(0,0)xy4x4+y4\lim_{(x, y) \to (0,0)} \frac{x \cdot y^4}{x^4 + y^4}

To evaluate this limit, we need to check if it tends to the same value along different paths as (x,y)(x, y) approaches (0,0)(0, 0). If the limit depends on the path, the overall limit does not exist.

Step 1: Evaluate the limit along y=0y = 0

If y=0y = 0, the expression becomes: x04x4+04=0\frac{x \cdot 0^4}{x^4 + 0^4} = 0 So, along the path y=0y = 0, the limit is 0.

Step 2: Evaluate the limit along x=0x = 0

If x=0x = 0, the expression becomes: 0y404+y4=0\frac{0 \cdot y^4}{0^4 + y^4} = 0 So, along the path x=0x = 0, the limit is also 0.

Step 3: Evaluate the limit along y=xy = x

If we substitute y=xy = x, the expression becomes: xx4x4+x4=x52x4=x2\frac{x \cdot x^4}{x^4 + x^4} = \frac{x^5}{2x^4} = \frac{x}{2} As x0x \to 0, x20\frac{x}{2} \to 0.

Step 4: Evaluate the limit along y=xy = -x

If we substitute y=xy = -x, the expression becomes: x(x)4x4+(x)4=xx4x4+x4=x52x4=x2\frac{x \cdot (-x)^4}{x^4 + (-x)^4} = \frac{x \cdot x^4}{x^4 + x^4} = \frac{x^5}{2x^4} = \frac{x}{2} Again, as x0x \to 0, x20\frac{x}{2} \to 0.

Conclusion:

Since the limit along multiple paths (e.g., y=0y = 0, x=0x = 0, y=xy = x, and y=xy = -x) all lead to the same result of 0, we conclude that the limit exists and is equal to 0.

Thus, the limit is: 0\boxed{0}

Would you like more details on any of the steps?

Here are 5 related questions:

  1. How do you evaluate limits in multivariable calculus using polar coordinates?
  2. What are the common strategies to prove a limit does not exist?
  3. How does the limit change when evaluated along different types of curves like y=x2y = x^2?
  4. How would this limit behave if the exponents in the denominator were different?
  5. What are some common pitfalls when evaluating limits in two variables?

Tip: When solving limits involving two variables, always check the behavior along multiple paths to ensure the limit is consistent.

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Math Problem Analysis

Mathematical Concepts

Multivariable Calculus
Limits of Functions of Two Variables
Path Dependency

Formulas

lim (x, y) → (0,0) [x*y^4 / (x^4 + y^4)]

Theorems

Pathwise Test for Multivariable Limits

Suitable Grade Level

University level (Calculus II or Multivariable Calculus)