Question

Given:
|4 -2| X = 2|-4 -4|
|-1 1| | 2 2|
What is X?

I solved this and couldn't get an answer - that is, the result was undefined/null, as it didn't like how the multiplication worked. I got this for every way I tried doing it, including by transposing the matrices and solving as per usual solve equation.

Is it actually just an equation with no answer, or am I missing something?

Answer 1

If you write this as

AX = B

then

X = A^{^-1}B
A^{^-1} =
(1 1)
(1 2)

now just crank it out.

Answer 2

oops - misspoke:
A^{^-1} =
1/2 (1 2)
(1 4)

So, X =
(0 0)
(4 4)

see

http://www.wolframalpha.com/input/?i=(inverse+%7B%7B4,-2%7D,%7B-1,1%7D%7D)*(2%7B%7B-4,-4%7D,%7B2,2%7D%7D)

Answer 3

Oooh, I forgot about inverse matrices. Thank you!