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Question

Let $f(x, y)$ be a continuously differentiable homogenous function of degree 4. Which of the following is necessarily true?

The correct answer is
$x \frac{\partial f(x, y)}{\partial x} + y \frac{\partial f(x, y)}{\partial y} = 4f(x, y)$

Homogeneous Function Degree 4 Solution

This problem involves Euler's Homogeneous Function Theorem, which relates a homogeneous function to its partial derivatives.

Euler's Theorem Statement

If $f(x, y)$ is a continuously differentiable homogeneous function of degree $n$, then it satisfies the following identity:

$x \frac{\partial f(x, y)}{\partial x} + y \frac{\partial f(x, y)}{\partial y} = n f(x, y)$

Applying to the Problem

The question states that $f(x, y)$ is a homogeneous function of degree 4. Thus, we have $n = 4$. Substituting $n=4$ into Euler's theorem gives:

$x \frac{\partial f(x, y)}{\partial x} + y \frac{\partial f(x, y)}{\partial y} = 4f(x, y)$

Result

This identity must necessarily be true for the given function. Comparing this result with the options provided, it matches Option 3.

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Important Questions from Algebra

  1. If $Pe^x = Qe^{-x}$ for all real values of $x$, which one of the following statements is true?
  2. The relationship between two variables $x$ and $y$ is given by $x + py + q = 0$ and is shown in the figure. Find the values of $p$ and $q$.
    Note: The figure shown is representative.

  3. The real variables $x, y, z$ and the real constants $p, q, r $ satisfy 
    $\frac{x}{pq - r^2} = \frac{y}{qr - p^2} = \frac{z}{rp - q^2}$
    Given the denominators are non-zero, the value of $px + qy + rz$ is

  4. The complex function 
    $e^{-\left(\frac{2}{z-1}\right)}$ 
    has __________________

  5. Consider two matrices: $P = \begin{bmatrix} 1 & 2 \\ 0 & 1 \end{bmatrix}$ and $Q = \begin{bmatrix} 1 & 0 \\ 1 & 0 \end{bmatrix}$. 
    Which of the following statement is/are true?

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