If X = [ α_ij ], i ≥ 1, j ≤ n, with α_ij = i - j. Then the number of linearly independent Rows are: 1. 0 2. 1 3. n 4. n - 1
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Understand the Problem
The question is asking for the number of linearly independent rows in a matrix defined by specific conditions. We need to analyze the properties of the matrix and determine the correct option from the given choices.
Answer
The number of linearly independent rows is $1$.
Answer for screen readers
The number of linearly independent rows is $1$.
Steps to Solve
- Understanding the matrix structure
The elements of the matrix $X = [\alpha_{ij}]$ are defined as $\alpha_{ij} = i - j$. This implies each element in the $i^{th}$ row and $j^{th}$ column is determined by the difference between the row index and the column index.
- Examining row dependencies
Consider rows of the matrix $X$. Each row $i$ can be expressed as: $$ R_i = [i - 1, i - 2, i - 3, \ldots, i - n] $$
This shows that each row can be rewritten based on its first element, which decreases linearly as $j$ increases.
- Generating the first few rows
If we write out a few rows, we get:
- For $i=1$: $[0, -1, -2, \ldots, 1-n]$
- For $i=2$: $[1, 0, -1, \ldots, 2-n]$
- For $i=3$: $[2, 1, 0, \ldots, 3-n]$
- Identifying linear dependence
Notice that any row can be formed by the previous row plus a fixed vector. For instance: $$ R_{i+1} = R_i + [1, 1, 1, \ldots, 1] $$ This structure leads to linear dependence, and specifically only one row can provide the unique information.
- Determining the number of linearly independent rows
Since all rows can be derived from each other through this linear combination, the number of linearly independent rows is limited.
Thus, after analyzing the structure, we can conclude that there is only 1 linearly independent row.
The number of linearly independent rows is $1$.
More Information
This result comes from the definition of the rows in the matrix. Since each row can be expressed as a linear combination of the others, the dimension of the row space is reduced to just one independent direction.
Tips
Common mistakes may include:
- Assuming more rows are independent without verifying the relationships between them.
- Not recognizing the linear dependence generated by the constant difference between rows.
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