Math Problem Statement

Calculate the determinant of the matrix \( D_n \), where \( d_{ij} \) is defined as follows: \[ d_{ij} = \begin{cases} n+1, & i = j \neq n, \\ n+1, & i = n \text{ and } j \neq n, \\ n+2, & i = j = n, \\ n, & \text{otherwise.} \end{cases} \]

Solution

The problem involves calculating the determinant of the matrix DnD_n, where the elements of the matrix dijd_{ij} are defined piecewise as follows:

\begin{cases} n+1, & i = j \neq n, \\ n+1, & i = n \text{ and } j \neq n, \\ n+2, & i = j = n, \\ n, & \text{otherwise.} \end{cases}$$ The matrix $$D_n$$ is a square $$n \times n$$ matrix. To solve for its determinant, we can follow these steps: --- 1. **Understand the Structure of $$D_n$$:** - Most entries of $$D_n$$ are $$n$$, except: - The diagonal elements are $$n+1$$, except for the last diagonal element, which is $$n+2$$. - The last row contains $$n+1$$ for all columns except the last one, which is $$n+2$$. 2. **Simplify the Matrix:** - Factorize or use row/column operations to simplify the computation of the determinant. 3. **Compute the Determinant Using Properties:** - The determinant of this matrix can often be calculated using cofactor expansion or a recursive formula for structured matrices. Would you like a detailed step-by-step computation for this determinant?

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Math Problem Analysis

Mathematical Concepts

Matrix Theory
Determinants
Linear Algebra

Formulas

Determinant calculation using cofactor expansion or row reduction

Theorems

Properties of determinants

Suitable Grade Level

Undergraduate Mathematics