- #1
SteliosVas
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Homework Statement
Okay I am given a matrix A = [2 1 ; 3 4]
The first step is to find numbers of a and b such that A2 + aA + bI = [0 0; 0 0]
I is an identity matrix (2x2).
Part B - After that is says to use the result of the above to express A5 as a linear combination of A and I
Homework Equations
Okay I am pretty sure for the first part it is just quite simply squaring A, putting the letter a and b in front of the respective matrix and multiplying.
Than equalling to 0 you have 2 unknowns and 4 equations solve for A and B.
As for the second part I am not sure if I should be using the characteristic polynomial or/and eigen values?
The Attempt at a Solution
Okay so for the first part i got 4 equations once eventually done the computations as:2a + b + 17 = 0
a + 6 = 0
3a+18=0
4a+b+19=0
Solving I get a = -6 and b = 5
Now for part B I am really stuck. . If i calculate the eigen values then, they are also the eigen values for A5.. Because I + A + A2... is an infinite series.. with a common ratio... Really stuck sure there is an easier way to look at it,