Question

Let M_(Z) denote the set of 2 x 2 matrices with integer entries, and let + denote matrix addition and denote matrix multiplication. Given [a b] a -b A al then A' гс 0 1 as the 0 element and the 1 element, respectively, either prove that 0 [MA(Z), +,,', 0, 1) is a Boolean algebra or give a reason why it is not.

Answer 1

To prove that the set [MA(Z), +', , 0, 1) forms a Boolean algebra, we need to show that it satisfies the following five axioms:

Closure under addition and multiplication: Given any two matrices A and B in MA(Z), both A+B and AB must also be in MA(Z).

Commutativity of addition and multiplication: For any matrices A and B in MA(Z), A+B = B+A and AB = BA.

Associativity of addition and multiplication: For any matrices A, B, and C in MA(Z), (A+B)+C = A+(B+C) and (AB)C = A(BC).

Existence of additive and multiplicative identities: There exist matrices 0 and 1 in MA(Z) such that for any matrix A, A+0 = A and A1 = A.

Existence of additive inverses: For any matrix A in MA(Z), there exists a matrix -A such that A+(-A) = 0.

To show that these axioms hold, we can do the following:

Closure under addition and multiplication: Let A=[a b; -a' a'] and B=[c d; -c' c'] be any two matrices in MA(Z). Then A+B=[a+c b+d; -a'-c' -b'-d'] and AB=[ac-ba' bd-ad'; -(ac'-ba') -(bd'-ad)]. Since the entries of A and B are integers, the entries of A+B and AB are also integers, so A+B and AB are both in MA(Z).

Commutativity of addition and multiplication: This follows directly from the properties of matrix addition and multiplication.

Associativity of addition and multiplication: This also follows directly from the properties of matrix addition and multiplication.

Existence of additive and multiplicative identities: Let 0=[0 0; 0 0] and 1=[1 0; 0 1]. Then for any matrix A=[a b; -a' a'] in MA(Z), we have A+0=[a b; -a' a'] and A1=[a b; -a' a'], so 0 and 1 are the additive and multiplicative identities, respectively.

Existence of additive inverses: For any matrix A=[a b; -a' a'] in MA(Z), let -A=[-a -

Step-by-step explanation: