# Easy matrix/determinants question

by astonmartin
Tags: None
 P: 23 1. The problem statement, all variables and given/known data Suppose A and B are 3 x 3 matrices and det A = x ≠ 0 while det B = y. Let C be the matrix ((2A)^-1 )B <-- (2A) inverse x B then det C is: 2. Relevant equations 3. The attempt at a solution det(2A) = 2x, so det 2A inverse = 1/(2x) det C = y/(2x)...which is not one of the solutions a) y/8x b) 2xy c) -2y/x d) 2y/x e) 8y/x what am I missing here?
 P: 26 You are very close; however, $$\det(\alpha A)=\alpha^{n} \det(A)$$ where n is the order of the matrix A, in this case 3. To understand why this happens, think of the determinant of the identity and multiply it by a scalar.

 Related Discussions Linear & Abstract Algebra 2 Calculus & Beyond Homework 2 Precalculus Mathematics Homework 7 Precalculus Mathematics Homework 2 Linear & Abstract Algebra 6