quick matrix question: absolute values of matrices...?

[mathfun]

A = [ 1 2
3 4]
B =
[-1 2
0 1]

Find
i) |A| ii) |2A| iii) |-A| iv) |-3B|

i checked my answers they are wrong. here are my anwsers.
i) 2 ii) 4 iii) 2 iv) 3

here are the answers i found at the back of my textbook.
i) -2 ii) -8 iii) -2 iv) -9

how can absolute values be negative? are does |A| does not mean absolute value in this case? ...does it simply mean the 'determinant'?

who's right?

 

[stapel]

Re: quick matrix question

how can absolute values be negative?

They aren't asking for absolute values. They're asking you to find the determinants. This really ought to have been covered in class, before they assigned homework on it.... :shock:

Eliz.

 

[mathfun]

hmm actually i changed school and matrices were suppose to be covered last year. however, it was not part of the curriculum in my old school so the teacher is giving us one month to self learn the matrix section.

 

[stapel]

I moved a lot when I was a kid. I know exactly what you're going through. You have my sympathies!

Eliz.