Let N be a nilpotent matrix of order 4 with real entries. Then which o...
Let N be a nilpotent matrix of order 4.
⇒ N4 = 0; N satisfied its characteristic equation
i.e λ4 = 0
λ = 0 eigenvalue of N
Since, eigenvalue of N4 is λ4 where λ is eigenvalue of N.
zero is the only eigenvalue as eigenvalue of N is all zero.
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Let N be a nilpotent matrix of order 4 with real entries. Then which o...
Explanation:
To determine the eigenvalues of a nilpotent matrix N, we need to understand the properties of nilpotent matrices.
Definition:
A matrix N is called nilpotent if there exists a positive integer k such that N^k = 0, where 0 is the zero matrix.
In other words, a nilpotent matrix N is a square matrix for which there exists a positive integer k such that N raised to the power of k is the zero matrix.
Now let's analyze the options one by one:
a) All eigenvalues are non-zero real numbers:
This statement is not true for nilpotent matrices. Since N is nilpotent, there exists a positive integer k such that N^k = 0. If all eigenvalues were non-zero real numbers, then the matrix N^k would have non-zero eigenvalues, which contradicts the fact that N^k is the zero matrix.
b) All eigenvalues are purely imaginary:
This statement is not true for nilpotent matrices either. Similar to the previous case, if all eigenvalues were purely imaginary, then N^k would have purely imaginary eigenvalues, which contradicts the fact that N^k is the zero matrix.
c) Zero is the only eigenvalue:
This statement is true for nilpotent matrices. Since N is nilpotent, there exists a positive integer k such that N^k = 0. This means that the characteristic polynomial of N, which is det(N - λI), must have λ = 0 as a root. Therefore, zero is the only eigenvalue of N.
d) At least one eigenvalue is real and at least one eigenvalue has a non-zero imaginary part:
This statement is also not true for nilpotent matrices. As mentioned earlier, if all eigenvalues were real or had a non-zero imaginary part, then N^k would have eigenvalues that do not satisfy these conditions, which contradicts the fact that N^k is the zero matrix.
Therefore, the correct answer is option 'c'. Zero is the only eigenvalue of a nilpotent matrix of order 4 with real entries.