# Inverse matrix

Cafka
Can someone verify this:

|1 -1| = P
|-2 1|

|-1 -1| For P^-1, i got this.
|-2 -1|

|-1 -2| My solutions manual, says this is the answer.
|-1 -1|

My solutions manual has been wrong before. The way i got my answer was to put the identity matrix to the right of P and solve for the right side and get the left into the identity.

|1 -1|1 0| = P
|-2 1|0 1|

|1 0|-1 -1| = P^-1
|0 1|-2 -1|

Thanks

Staff Emeritus
Gold Member
A good way to check your work is to multiply the two matrices together (P, and what you get for P^-1) and check if you get the identity back.

If you do for your matrix and not that in the answer book, you can be confident you did it right.

Cafka
Hurkyl said:
A good way to check your work is to multiply the two matrices together (P, and what you get for P^-1) and check if you get the identity back.

If you do for your matrix and not that in the answer book, you can be confident you did it right.
Yeah, i multiplied them back and they went ot the identity matrix.

Staff Emeritus