How do you find the inverse of a 3x3 Matrix??

[mAdD INDIAN]

How do you do it using determinants??

I know how to do it using the echelon method, but that takes too long and is quite hard (for me atleast, I hate echelon!!)

 

[Capn]

I want to say it's 1/det(matrix)*[matrix transverse], but I graduated in december and am now on permanent vacation, so don't quote me on that.

 

[mAdD INDIAN]

Thats how you do it for a 2x2 Matrix? thanks anyway...but I need it for a 3x3

 

[KEV1N]

It works for a matrix of any size

 

[mAdD INDIAN]

so if I had a Matrix like this:

a d g
b e h
c f i

What would its Determinant be?? Wouldn't it be
a(ei - hf) - d(bi - hc) + g(bf - ec) ???

 

[abaez]

is echelon doing it where you get 1 0 0
0 1 0
0 0 1?

cause that way is easy

 

[Valhalla1]

do what i did on all my high school algebra matrices test -

plug it into your ti-85 and raise it to the -1

 

[mchammer187]

adjoint/ determinant

i believe dont quote me tho

 

[crypticlogin]

I actually remembered this from college, but this guy was kind enough to type it up for me.

3x3 matrix inverse from determinants

 

[ViperVin2]

<< so if I had a Matrix like this:

a d g
b e h
c f i

What would its Determinant be?? Wouldn't it be
a(ei - hf) - d(bi - hc) + g(bf - ec) ??? >>



yes

i think so

 

[PsychoAndy]

I'd go with Valhalla, raise it to the -1 on the matrix.

 

[mchammer187]

<< I actually remembered this from college, but this guy was kind enough to type it up for me.

3x3 matrix inverse from determinants >>




i guess i was right

maybe i did learn something in differential equations w/ linear algebra