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November 10th, 2015, 11:01 PM  #1 
Newbie Joined: Jan 2014 Posts: 10 Thanks: 0  Computation of matrix inverse: I + A
Let I be the identity matrix, and A be an invertible matrix. Suppose A^(1) is given. How can we cheaply compute (A + I)^(1) Can you help me find the right identity. Thank you so much in advance. 
November 11th, 2015, 11:59 AM  #2 
Banned Camp Joined: Mar 2015 From: New Jersey Posts: 1,720 Thanks: 125 
Solve (A+I)B=I for B For 1X1 matrix solve (a+1)b=1. It has no simple solution in terms of 1/a so OP is not generally solvable. 
November 12th, 2015, 05:05 AM  #3 
Newbie Joined: Jan 2014 Posts: 10 Thanks: 0 
Hi. I can't see how (A+I)B = I makes computation of (A+I)^(1) cheaper. How do i exploit that that A^(1) is known? Thanks in advance 

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computation, inverse, matrix 
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