Solution Found!
We call the vector x Rn integral if every component xi is an integer. Let A be a
Chapter 5, Problem 8(choose chapter or problem)
We call the vector \(\mathbf{x} \in \mathbb{R}^{n}\) integral if every component \(x_i\) is an integer. Let A be a nonsingular \(n \times n\) matrix with integer entries. Prove that the system of equations Ax = b has an integral solution for every integral vector \(\mathbf{b} \in \mathbb{R}^{n}\) if and only if det A = \(\pm 1\). (Note that if A has integer entries, \(\mu_{A}\) maps integral vectors to integral vectors. When does \(\mu_{A}\) map the set of all integral vectors onto the set of all integral vectors?)
Questions & Answers
QUESTION:
We call the vector \(\mathbf{x} \in \mathbb{R}^{n}\) integral if every component \(x_i\) is an integer. Let A be a nonsingular \(n \times n\) matrix with integer entries. Prove that the system of equations Ax = b has an integral solution for every integral vector \(\mathbf{b} \in \mathbb{R}^{n}\) if and only if det A = \(\pm 1\). (Note that if A has integer entries, \(\mu_{A}\) maps integral vectors to integral vectors. When does \(\mu_{A}\) map the set of all integral vectors onto the set of all integral vectors?)
ANSWER:Problem 8
We call the vector integral if every component is an integer. Let be a non – singular matrix with integer entries. Prove that the system of equations has an integral solution for every integral vectorif and only if
Step by Step Solution
Step 1 of 3
For an matrix A, the solution of the system of equations is
(i)
Now, the solution is an integral whenever is integral
It is already given that is integral. Since, product of two integral is an integral, therefore, it is enough to prove that is an integral if and only if .