I have the following problem:
I have 2 3x3 matrices, on called M and the other N^-1 (this one has a few unknown numbers, k). I am asked to find the following:
(MN)^-1. Now we have NOT learned how to do the inverse of 3x3 matrices yet, so there must be some other way of solving this...but how?
M=
(3 0 8
0 2 0
1 0 4)
and N^-1=
(1 -2 3
3 k 0
2 4 k)
Please help...
Thanks a lot for the helpful formula...
The only problem is that this question is one our teacher has given us, meaning we SHOULD be able to solve it...without a calculator. And I'm actually not supposed to use the formula you said either...(just realised the question states this)
Isn't there some way I could do that?
HGello, Helena!
If that's true, we can still solve it.Given: .
Find
Now we have NOT learned how to do the inverse of 3x3 matrices yet, . (Really?)
so there must be some other way of solving this ... but how?
We know: . . . . and we need
We can find it the old-fashioned way . . .
Let: .
Then: .
Hence: .
And we have a system of equations: .
. . which we can solve: .
And we have: .
Got it?