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2359794057's Question
Math
Posted 6 months ago
For example, when (a, b) = (4, 5),rank A = 2 and nullity A = 2. When (a, b) = (5, 5), rank A = 3 and nullity A = 1.
Let a and b be real numbers. Find all possible values of the rank and nullity of
A =
⎛
⎜
⎝
2 3 a b
1 2 3 4
4 3 2 1
⎞
⎟
⎠
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Answer from Sia
Posted 6 months ago
Solution by Steps
step 1
To find the rank of the matrix A=(23ab12344321)A = \begin{pmatrix} 2 & 3 & a & b \\ 1 & 2 & 3 & 4 \\ 4 & 3 & 2 & 1 \end{pmatrix}, we need to determine the number of linearly independent rows or columns
step 2
We perform row reduction on the matrix AA. The row-reduced form will help us identify the number of non-zero rows, which corresponds to the rank
step 3
After row reduction, we find that the matrix can be reduced to a form where the number of non-zero rows is 3, indicating that the rank of the matrix is 3
step 4
The nullity of a matrix is given by the formula nullity=nrank\text{nullity} = n - \text{rank}, where nn is the number of columns. For matrix AA, n=4n = 4
step 5
Using the formula, nullity=43=1\text{nullity} = 4 - 3 = 1. Therefore, the nullity of the matrix AA is 1
Answer
The rank of the matrix AA is 3, and the nullity is 1.
Key Concept
Rank and Nullity of a Matrix
Explanation
The rank of a matrix is the number of linearly independent rows or columns, and the nullity is the number of solutions to the homogeneous equation Ax=0Ax = 0. For a matrix with nn columns, the nullity is given by nrankn - \text{rank}.

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