Math Problem Statement
If matrices A, B and C are all non-zero matrices, are statements I and II true or false?
Statement I: AB = BC implies A = C.
Statement II: AB = AC implies B = C.
Explain, or give examples to justify your answer.
Solution
Let's analyze each statement one by one.
Statement I: AB = BC implies A = C.
This statement is false in general. To understand why, we can explore a counterexample.
Example:
Let: Now, calculate and : So, , but , because is a row matrix, and is also a row matrix, but they are the same in this case purely due to coincidence with the dimensions and entries. In general, the equality does not imply that .
Statement II: AB = AC implies B = C.
This statement is false in general as well. The key reason is that if is a non-invertible (singular) matrix, then it's possible for to hold without .
Example:
Let: Now calculate and : So, , but . This happens because is the zero matrix, and multiplying anything by the zero matrix results in the zero matrix, hence the equality holds but without and being equal.
Conclusion:
- Statement I is false because does not imply .
- Statement II is false because does not imply , especially when is singular (non-invertible).
Would you like more details or have any questions about these concepts? Here are some related questions to explore further:
- What is the condition for to imply ?
- Under what conditions can imply ?
- How does matrix invertibility affect the validity of these statements?
- What is the concept of matrix rank and how does it relate to these properties?
- What does it mean for a matrix to be singular or non-invertible?
Tip: A matrix is invertible if and only if its determinant is non-zero. Understanding this property can help determine conditions under which matrix equations like and hold.
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Math Problem Analysis
Mathematical Concepts
Matrix Multiplication
Linear Algebra
Matrix Properties
Formulas
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Theorems
Matrix equality
Non-invertible matrix behavior
Suitable Grade Level
Grades 11-12