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AMM #2
| Question | Answer |
|---|---|
| How to calculate determinant of 2x2 matrix | det(M)= ad - bc |
| How to calculate determinant of 3x3 matrix | rewrite first two columns then calculate product of \+\+\ and subtract /-/-/ |
| What happens to determinant if we change two rows or columns | the determinant change its sign |
| What is property of determinant 1, in traspose matrix 2, multiplying every element by k | 1, in traspose matrix is the same as original matrix det(A)=det(A´) 2, multiplying every element by k it multiplying by k^n where n is dimension of matrix det(kA)= k^n det(A) |
| What happend to matrix determinant if we add/subtract other rows/column within a matrix | it stays unchanged |
| What is determinant 1,det(I) 2,det(AB) 3, det(A^-1) 4,det(A+B) 5,det(triangular / diagonal) | 1,det(I) = 1 2,det(AB) = det(A)*det(B) 3, det(A^-1) = 1/det(A) 4,det(A+B) ≠ det(A) + det(B) 5,det(triangular / diagonal) = Π diagonal elements |
| How to calculate the inverse matrix | for each element b(i,j) b(i,j)= 1/ det(A) * (-1)^(i+j) * det(Aij) where (Aij) is the determinant of matrix without current row and column |
| What is linear combination | linear combination = scaled vectors added together (0) (1)* 3 & (1) (0)*2 = (2) (3) |
| What is linear dependence of vectors | when c1v1+c2v2+..ckvk=0 if at least ine vector can be build as combination or multiplication of others vectors (only for non-trivial so c≠0) |
| What is rank of the matrix (3) | 1, if matrix is divided into rows or columns how many of them are maximaly independent 2, nr. of ind. row = nr. of ind. col. 3, if non-singular rk(A) = n |
| Can rank be calculated for non-sqaure matrices | yes, not as determinant it can be calculated also for rectangular matrices |
| What are 3 properties of matrix rank | 1, exchanging rows or columns does not change the rank 2, rk(A)=rk(A´) 3,rk(A)= rk(A´A) |
| How to determine the rank of the matrix (3) | 1, with Eigenvalues 2, with Gaussian algorithm 3, finding the largest sqaure submatrix whose derminant is not zero >> its size gives the rank |
| How to solve linear equation with matrix notation | A.. matrix with n x k x ... unknown coefficient vector with k x 1 b... result vector with n x 1 |