Question

Is the matrix [1 2 3 4] invertible?
That is the matrix is 1 2 on the top row and 3 and 4 on the bottom row

Answer 1

check that the determinant is not zero. and it isn't, so you can invert this easily

Answer 2

a b
c d
----

do ad-bc

Answer 3

and your inverse is


d -b
-c a

all divided by the determinant

Answer 4

that's right! :)

Answer 5

so the inverse is
[-2 1
3/2 -2 ]

Answer 6

the last entry is suppose to be -1/2

Answer 7

thank you!