4. Let A be an m × n matrix. Show that ker(A)-ker(A*A) Hints: (a) In general,...
100 GAUSSIAN ELIMINAONO the system Ax = b (where A is n × n and nonsingular), MATLAB uses Gaussian elimination with partial pivoting to solve the system. If you want to see the LU decomposition, use the MATLAB command lu. Exercise 1.8.10 Use MATLAB to check the LU decomposition obtained in Example 1.8.2 Enter the matrix A, then type [L, U, P] = lu (A) . Once you have L, U, and P, you can put them back together by...
Let A be an m × n matrix, let x Rn and let 0 be the zero vector in Rm. (a) Let u, v є Rn be any two solutions of Ax 0, and let c E R. Use the properties of matrix-vector multiplication to show that u+v and cu are also solutions of Ax O. (b) Extend the result of (a) to show that the linear combination cu + dv is a solution of Ax 0 for any c,d...
4. Suppose T :V →V is linear. Suppose that R(T) n ker(T) = {Ov}. Let {V1, ..., Vx} be a basis for ker(T) and {W1, ..., Wn} be a basis for R(T). (a) (8 marks) Show that the set {V1, ..., Uk, W1, ..., Wn} is linearly independent. HINT: you might start by assuming that Civi+...+ CkUk + ajwi + ... + anwn = 0 Apply T to both sides of this equation. What can you say about Q1W1+... +...
1. Let A be an m x n matrix. Determine whether each of the following are TRUE always or FALSE sometimes. If TRUE explain why. If FALSE give an example where it fails. (a) If m n there is at most one solution to Ax = b. always solve Ax b (b) If n > m you can (c) If n > m the null space of A has dimension greater than zero. (d) If n< m then for some...
A8.2 Let A be an m × n matrix and B be an n × p matrix. (a) Show that col(B) C null(A) if and only if AB = 0. (b) Show that if AB = 0, then rank(A) + rank(B) 〈 n.
A8.2 Let A be an m × n matrix and B be an n × p matrix. (a) Show that col(B) C null(A) if and only if AB = 0. (b) Show that if AB = 0,...
12.3 Least angle property of least squares. Suppose the m × n matrix A has linearly independent columns, and b is an m-vector. Let x ATb denote the least squares approximate solution (a) Show that for any n-vector a, (Ax)Tb - (Aa)"(Aâ), i.e., the inner product of Ax and b is the same as the inner product of Ax and Ai. Hint. Use (Ax)b (ATb) and (ATA)2 = ATb (b) Show that when A and b are both nonzero, we...
7. Let A be a 4 x 3 matrix, and let b and y be two arbitrary vectors in R. We are told that the system Ax- b has a unique solution. What can you say about the number of solutions of the system Ax - y? Explain your answer. 8. Let u. v, w, b be arbitrary vectors in R". Suppose that b = x1u+xy+23w for some scalars i, r23. Show that Span u, v, w, b Span u,...
A1. Let (A, B, C, D) be a SISO system in which A is a (n x n) complex matrix and B a (n x 1) column vector, let -1 V = {£ajA*B: aj e C; j= 0, ...,n- (i) Show that V is a complex vector space. (ii) Show that V has dimension one, if and only if B is an eigenvector of A AX for X E V. Show that S defines a linear map from S: V...
4. Let A be an n x n matrix. Define the trace of A by the formula tr(A) = 2 . In other words, the trace of a matrix is the sum of the diagonal entries of the matrix. It is known that for two n x n matrices A and B, the trace has the property that tr(AB) = tr(BA). Each of the following holds more generally, for n x n matrices A and B, but in the interest...