Simple Matrix Math Problem help

[rinny]

I've tried to solve this matrix countless ways and I cant seem to match the answer in the back of the book.

Here it is:

(I + 2A)^-1 = (-1 4 : 2 5)


The way I solved, or, didnt solve:
a) Distribute -1 into brackets leaving I^-1 + (2A)^-1 = RS
b) Subtract I^-1 from RS...I being equal to (1 0: 0 1)

This gives (0 2: 4 4)
c) You now have (2A)^-1 = (0 2: 4 4)
Inverse each side giving 2A = (0 2: 4 4)^-1
Which results in 2A = (4 -4 : -2 0) x (-1/8) --Determinant

d) Divide RS by 2

My answer is wrong so no point in posting it, as is my procedure I'd guess.


The answer in the book is:

(-9/13 2/13: 1/13 -6/13)


Any insight is appreciated!

[Markov7]

Here you go bro.

(I+2A)^-1 = [-1 4 : 2 5]

(I + 2A) = -1/13*[5 -4 : -2 -1] <----- (Inverse)

2A = [-5/13 4/13 : 2/13 1/13] - [1 0 : 0 1]


2A = [-18/13 4/13 : 2/13 -12/13]

A = [-9/13 2/13 : 1/13 -6/13]

[rinny]

Got it. Thanks for the help Markov, it was just a small error ( but big error in concept) that I had made

[dsr7723]

Question 1: Do you guys ever get laid?

Question 2: Where in the blue flying fuck are you ever gonna use that stuff in the real world?

[Markov7]

Originally posted by dsr7723
Question 1: Do you guys ever get laid?

Question 2: Where in the blue flying fuck are you ever gonna use that stuff in the real world?

Hahaha, i just love when people post shit like this. I agree to some extent that this stuff isn't very practical but it was a course i needed to take.

[Little Dragon]

Originally posted by dsr7723
Question 1: Do you guys ever get laid?

Question 2: Where in the blue flying fuck are you ever gonna use that stuff in the real world?

The hell is wrong with you.
The guy needed help with a question, no need to be an asshole.

[Disoblige]

^^
:werd:



Originally posted by dsr7723
Question 1: Do you guys ever get laid?

Question 2: Where in the blue flying fuck are you ever gonna use that stuff in the real world?

I love it when people like this post this as well. Yeah you won't use this kind of calculations in real life because computers can do it way faster, but you need to understand the concept behind this depending on what field you are in.

lol @ whatever getting laid has to do with this..

[Critical]

Originally posted by dsr7723
Question 2: Where in the blue flying fuck are you ever gonna use that stuff in the real world?
I've used matrices for encryption and animation. :nut:

[davidI]

Originally posted by dsr7723
Question 1: Do you guys ever get laid?

Question 2: Where in the blue flying fuck are you ever gonna use that stuff in the real world?

I'm not an engineer but find it funny when people think stuff like this and then 10 years later they're living in a basement suite while the Engineer is living it up in a nice house with a hottie.