Matrix help!

[Guest]

I am stuck on these problems:

A = [ 5 7 ] A^-1 = [ a b ]
[ 7 10] , then [ c d ] , c =

would c = -7?

and......

A = [ 5 7 ]
[ 0 10 ] [ [3 2 ]

and then AXB will have which of the following:

b = [ 1 0 3 ]
[ 2 1 0 ]

3 rows and 3 columns
2 rows and 3 columns
3 rows and 2 columns
2 rows and 2 columns
none listed

Now I think it is 2 rows and 2 colums, but I am not forsure.

 

[stapel]

1) Yes.

2) Sorry; can't figure this one out. Please use the "code" tags to fix placement of characters, or use LaTeX or one of the other suggested formats (explained in the links in the "Forum Help" pull-down menu at the very top of the page).

Thank you.

Eliz.

 

[rachael724]

I wil try to help you......

 

[Guest]

I am stuck on these problems:

A = [ 5 7 ] A^-1 = [ a b ]
[ 7 10] , then [ c d ] , c =

would c = -7?

and......

A = [ 5     7 ]                
      [ 0    10 ]                                                                                                    [     [3     2  ]

and  then AXB will have which of the following:

 b = [  1   0  3 ]
       [   2   1  0 ] 

3 rows and 3 columns    
2 rows and 3 columns    
3 rows and 2 columns    
2 rows and 2 columns    
none listed

Now I think it is 2 rows and 2 colums, but I am not forsure.

 

[soroban]

Hello, adam40g!

I'll take a guess at the second problem . . .

Given: . \(\displaystyle A\:=\:\left|\begin{array}{ccc}5 & 7 \\ 0 & 10 \\ 3 & 2\end{array}\right|\) .and . \(\displaystyle B\:=\:\left|\begin{array}{ccc}1 & 0 & 3 \\ 2 & 1 & 0\end{array}\right|\)

then \(\displaystyle A\times B\) will have which of the following:

a) 3 rows and 3 columns
b) 2 rows and 3 columns
c) 3 rows and 2 columns
d) 2 rows and 2 columns
e) none listed

. . . . . . . . . . . . . The inner numbers must match
We are multiplying a \(\displaystyle [\underbrace{3\times\overbrace{2]\text{ by a }[2}\times3}]\)
. . . . . . . The outer numbers give the dimensions of the product

The answer will be a \(\displaystyle 3\times3\) determinant . . . answer (a)