Solutions 227
A 2 = Al = (A--lf =
00^
00 0
00 0
=> dimM(Ai) = 3 - rank(Ai) = 3-1 = 2.
A\ = 0 => rfim7V(yl?) = 3 =>• m = 3, m(s) = f s - — J.
Choose v 3 e Af(Al) 9» 2 = AiV 3 ^6 ^ Afv 3 = ui-
t; 3 = e^ = (0,0,l)J => v 2 = A 1 v 3 = 0,— ,0
Thus,
A^10 =
1010
5 =
1 10 45
0 1 10
0 0 1
1
00 ool
0^0
0 01
=
- 1
100
0
0
=>
00"
TO 0
0 1_
10'
S~lAS
Vi = A\V 2
Vioo
,0,0
in -^1 -
10
10
10 J-
10 J
10
100
10
1
= Syl^10 ^-^1.
Note that the calculation of A^10 is as hard as that of A^10 since A is not
diagonal. However, because (easy to prove by induction)
A" (i)A"-^1 Q)A"-^2
A" (^)A"-^1
An
[A 1 1
A 1
A
n
=
we have
A^10 =
(^)°io(^)
9
«(^)
8
(TO)^10 IO(^)
(TO)^10.
10 10
1 100 4500
0 1 100
0 0 1
Hence, it is still useful to have Jordan decomposition.
4.4 (a)
—— = -0.03Yi - 0.02F 2 —- = -0.04Yi - 0.0iy 2
at at
^ = -0.05.Yi - 0.02X 2 ~ = -0.03Xi - 0.00X 2
at at
Let WT = [Xi,X2,Yi,Y 2 }. Then, the above equation is rewritten as
dW
dt
= AW,