Some linear algebra problems i with

skybluekitty
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Let A and B be nxn matrices.
1. Suppose that AB=AC and det A does not equal 0. Show that B=C

2. Show that A is nonsingular if and only if A transpose is nonsingular.

3. Show that det AB = det BA.

4. Show that det AB = 0 if and only if det A=0 or det B=0

5. Show that if AB= -BA and n is odd, then A or B is singular.

6. Show that det A*Atranspose is greater than equal to 0

7. Show that det A*Btranspose = det Atranspose* det B

8. Let A be nxn skew-symmetric matrix. If n is odd, show that det A=0

9. Show that 3x3 vandermonde matrix has a determinant equal to (a-b)(b-c)(c-a) The matrix is
[1 1 1
a b c
a^2 b^2 c^2]
Thank you.


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There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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