Matrix polynomials and inverses- Linear Algebra

In summary, we are given a polynomial p(x)=x4-2x3+3x2-3x+1 and a matrix A with the values of 1, 1, 1, -1, -1, 0, -2, 1, 0, 0, 1, 0, and 1, 0, 0, 0. By checking that p(A)=0, we can find a polynomial q(x) such that q(A)=A-1. The purpose of p(x) is not relevant at this point. Using the fact that A(-A3+2A2-3A+3I)=I, we can determine that q(x)
  • #1
lina29
85
0

Homework Statement


For p(x)=x4-2x3+3x2-3x+1 and

A= 1 1 1 -1
-1 0 -2 1
0 0 1 0
1 0 0 0

you can check that P(A)=0 using this find a polynomial q(x) so that q(A)=A-1. The point is A4-2A3+3A2-3A=A(-A3+2A2-3A+3I)=I

a) What is q(x)?

I don't really understand how to approach this problem. My initial though was that I had to solve the right side of the eqn(A4-2A3+3A2-3A) and that would be q(x). Am I on the right track? Also what's the purpose of p(x)?
 
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  • #2
Well, you say, or were given, that "the point is [itex]A(-A^3+2A^2- 3A+ 3I)= I[/itex]

Isn't the definition of "inverse" that [itex]AA^{-1}= I[/itex]?
 
  • #3
lina29 said:

Homework Statement


For p(x)=x4-2x3+3x2-3x+1 and

A= 1 1 1 -1
-1 0 -2 1
0 0 1 0
1 0 0 0

you can check that P(A)=0 using this find a polynomial q(x) so that q(A)=A-1. The point is A4-2A3+3A2-3A=A(-A3+2A2-3A+3I)=I

a) What is q(x)?

I don't really understand how to approach this problem. My initial though was that I had to solve the right side of the eqn(A4-2A3+3A2-3A) and that would be q(x). Am I on the right track? Also what's the purpose of p(x)?

Try to be more consistent with your letters. The functions you're working with are named p and q, so you shouldn't be using P in place of p. p(x) = x4-2x3+3x2-3x+1, so p(A) = A4-2A3+3A2-3A+I. Don't worry about the purpose of p - just take it as given for now.

You have A(-A3+2A2-3A+3I) = I. If A times whatever is the identity, then the whatever is the inverse of A. q(A) will be the inverse of A.
 

1. What are matrix polynomials and inverses in Linear Algebra?

Matrix polynomials and inverses are mathematical concepts used in linear algebra to solve systems of equations. A matrix polynomial is a function that takes a matrix as its input and returns a new matrix as its output. The inverse of a matrix is a matrix that, when multiplied by the original matrix, results in the identity matrix.

2. How do you find the inverse of a matrix polynomial?

To find the inverse of a matrix polynomial, you can use the determinant and adjugate matrix method. First, you must calculate the determinant of the matrix polynomial, and then find the adjugate matrix by transposing the matrix of cofactors. Finally, divide the adjugate matrix by the determinant to find the inverse matrix.

3. What is the purpose of finding the inverse of a matrix polynomial?

The inverse of a matrix polynomial is useful in solving systems of equations, as it allows you to find the solution by multiplying both sides of the equation by the inverse matrix. It can also be used to find the inverse of a linear transformation, which is important in many applications of linear algebra.

4. Can all matrix polynomials be inverted?

No, not all matrix polynomials can be inverted. A matrix polynomial can only be inverted if its determinant is non-zero. If the determinant is zero, the matrix is said to be singular, and no inverse exists.

5. How are matrix polynomials and inverses used in real-world applications?

Matrix polynomials and inverses have many real-world applications, such as in computer graphics, economics, and physics. They are used to solve systems of equations, model and analyze complex systems, and make predictions based on data. Inverses are also used to find the best fit line for a set of data points, which is important in statistics and data analysis.

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