### Matrix Questions

1.(a) If A is invertible and AB = AC, prove that B = C. (b) Let A =24 1 1 1 135 explain why A is not invertible. (c) Let A =24 1 1 1 135, ¯nd 2 matrices B and C, B 6= C such that AB = AC. 2. (a) If a square matrix A has the property that row 1 + row 2 = row 3, clearly explain why the matrix A is not invertible. (b)