Matrix Homework: Solving for B in Statement 5

In summary: B, such that A^2B= A for all non-singular matrices, A, we can disprove part c. In summary, part a is easy, part b is different from part a, and part c is not correct. Part d is the prove, and part e is how to disprove part c.
  • #1
athrun200
277
0

Homework Statement


See question 5


Homework Equations





The Attempt at a Solution



For part a, it is very easy.
Multiply the inverse of A 2 times on both side, we can see the B=inverse of A.
i.e. The required B is inverse of A, then the proof is finished.

But how about part b?
It seems it is the same part a.

Is part b also correct?
 

Attachments

  • 11aAss1.pdf
    131.2 KB · Views: 229
Physics news on Phys.org
  • #2
Part b is quite different from part a- and the difference is important to learn. Mathematics must be very very precise in its wording- unlike science we don't have observations and experiments to fall back on. In other words, we can't just look at the real world- words are everything!

In part a it ask if, given a non-singular matrix A, there exist a matrix B such that [itex]AB^2= A[/itex]. You are right- just multiply, on the left, on both sides by [itex]A^{-1}[/itex], which exists because A is non-singular, and the equation becomes AB= I. Yes, B exists and is the inverse of A.

In part B, it asks if there exists a matrix B such that, for any non-singular matrix, A, [itex]A^2B= A[/itex]. "Any" is the crucial word there. Is there a single matrix B that is the inverse of all invertible matrices?
 
  • #3
HallsofIvy said:
Part b is quite different from part a- and the difference is important to learn. Mathematics must be very very precise in its wording- unlike science we don't have observations and experiments to fall back on. In other words, we can't just look at the real world- words are everything!

In part a it ask if, given a non-singular matrix A, there exist a matrix B such that [itex]AB^2= A[/itex]. You are right- just multiply, on the left, on both sides by [itex]A^{-1}[/itex], which exists because A is non-singular, and the equation becomes AB= I. Yes, B exists and is the inverse of A.

In part B, it asks if there exists a matrix B such that, for any non-singular matrix, A, [itex]A^2B= A[/itex]. "Any" is the crucial word there. Is there a single matrix B that is the inverse of all invertible matrices?

Well, after listening to your explanation, I know part b is obvious wrong.
However, I wonder how to write it out.
 
  • #4
"No, there does not exist a single matrix, B, such that [itex]A^2B= A[/itex] for all non-singular matrices, A."
 
  • #5
HallsofIvy said:
"No, there does not exist a single matrix, B, such that [itex]A^2B= A[/itex] for all non-singular matrices, A."

Oh, this is the prove?
 
  • #6
Let me try for part d.

Since [itex]A[/itex] is non-singular, [itex]A^{-1}[/itex] exists.
So [itex]\vec{x}[/itex]=[itex]A^{-1}[/itex][itex]\vec{y}[/itex] exists.

So, there exists [itex]\vec{x}[/itex] s.t. [itex]A[/itex][itex]\vec{x}[/itex]=[itex]\vec{y}[/itex]

Again, how to disprove part c?
By simply saying NO, there doesn't exist?
 

Related to Matrix Homework: Solving for B in Statement 5

What is "Matrix Homework: Solving for B in Statement 5"?

"Matrix Homework: Solving for B in Statement 5" is a type of math problem that involves solving for the variable B in a matrix equation. It is a common assignment in math classes and requires knowledge of matrix operations and algebraic equations.

Why is solving for B in Statement 5 important?

Solving for B in Statement 5 is important because it helps to understand how matrix equations work and how to manipulate them to find the value of a specific variable. It also helps to develop problem-solving skills and logical thinking.

What are the steps for solving for B in Statement 5?

The steps for solving for B in Statement 5 may vary depending on the specific matrix equation given, but generally, the steps involve simplifying the equation, isolating the B variable on one side, and solving for B using inverse operations.

What are some tips for solving for B in Statement 5?

Some tips for solving for B in Statement 5 include making sure to follow the order of operations, checking your work for errors, and practicing with different types of matrix equations to improve your skills.

What are some common mistakes when solving for B in Statement 5?

Some common mistakes when solving for B in Statement 5 include forgetting to distribute or combine like terms, making errors with negative signs, and miscalculating during the simplification process. It is important to double-check your work and be mindful of any potential mistakes.

Similar threads

  • Precalculus Mathematics Homework Help
Replies
7
Views
2K
  • Precalculus Mathematics Homework Help
2
Replies
57
Views
3K
  • Precalculus Mathematics Homework Help
Replies
4
Views
1K
  • Precalculus Mathematics Homework Help
Replies
18
Views
2K
  • Precalculus Mathematics Homework Help
Replies
9
Views
2K
  • Precalculus Mathematics Homework Help
Replies
15
Views
4K
  • Precalculus Mathematics Homework Help
Replies
5
Views
1K
  • Precalculus Mathematics Homework Help
Replies
4
Views
1K
  • Precalculus Mathematics Homework Help
Replies
18
Views
2K
  • Precalculus Mathematics Homework Help
Replies
18
Views
2K
Back
Top