1. is Periodic Matrix ?
[1-2-6-32920-3]Solution:A square matrix A is called a periodic matrix, if Am=A for some positive integer m.
= | | 1×1-2×-3-6×2 | 1×-2-2×2-6×0 | 1×-6-2×9-6×-3 | | | -3×1+2×-3+9×2 | -3×-2+2×2+9×0 | -3×-6+2×9+9×-3 | | | 2×1+0×-3-3×2 | 2×-2+0×2-3×0 | 2×-6+0×9-3×-3 | |
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= | | 1+6-12 | -2-4+0 | -6-18+18 | | | -3-6+18 | 6+4+0 | 18+18-27 | | | 2+0-6 | -4+0+0 | -12+0+9 | |
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= | | -5×1-6×-3-6×2 | -5×-2-6×2-6×0 | -5×-6-6×9-6×-3 | | | 9×1+10×-3+9×2 | 9×-2+10×2+9×0 | 9×-6+10×9+9×-3 | | | -4×1-4×-3-3×2 | -4×-2-4×2-3×0 | -4×-6-4×9-3×-3 | |
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= | | -5+18-12 | 10-12+0 | 30-54+18 | | | 9-30+18 | -18+20+0 | -54+90-27 | | | -4+12-6 | 8-8+0 | 24-36+9 | |
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Here
A3=A, so
A is a periodic matrix of period 2
2. is Periodic Matrix ?
[2-2-6-32920-3]Solution:A square matrix A is called a periodic matrix, if Am=A for some positive integer m.
= | | 2×2-2×-3-6×2 | 2×-2-2×2-6×0 | 2×-6-2×9-6×-3 | | | -3×2+2×-3+9×2 | -3×-2+2×2+9×0 | -3×-6+2×9+9×-3 | | | 2×2+0×-3-3×2 | 2×-2+0×2-3×0 | 2×-6+0×9-3×-3 | |
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= | | 4+6-12 | -4-4+0 | -12-18+18 | | | -6-6+18 | 6+4+0 | 18+18-27 | | | 4+0-6 | -4+0+0 | -12+0+9 | |
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= | | -2×2-8×-3-12×2 | -2×-2-8×2-12×0 | -2×-6-8×9-12×-3 | | | 6×2+10×-3+9×2 | 6×-2+10×2+9×0 | 6×-6+10×9+9×-3 | | | -2×2-4×-3-3×2 | -2×-2-4×2-3×0 | -2×-6-4×9-3×-3 | |
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= | | -4+24-24 | 4-16+0 | 12-72+36 | | | 12-30+18 | -12+20+0 | -36+90-27 | | | -4+12-6 | 4-8+0 | 12-36+9 | |
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= | | -4×2-12×-3-24×2 | -4×-2-12×2-24×0 | -4×-6-12×9-24×-3 | | | 0×2+8×-3+27×2 | 0×-2+8×2+27×0 | 0×-6+8×9+27×-3 | | | 2×2-4×-3-15×2 | 2×-2-4×2-15×0 | 2×-6-4×9-15×-3 | |
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= | | -8+36-48 | 8-24+0 | 24-108+72 | | | 0-24+54 | 0+16+0 | 0+72-81 | | | 4+12-30 | -4-8+0 | -12-36+45 | |
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= | | -20×2-16×-3-12×2 | -20×-2-16×2-12×0 | -20×-6-16×9-12×-3 | | | 30×2+16×-3-9×2 | 30×-2+16×2-9×0 | 30×-6+16×9-9×-3 | | | -14×2-12×-3-3×2 | -14×-2-12×2-3×0 | -14×-6-12×9-3×-3 | |
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= | | -40+48-24 | 40-32+0 | 120-144+36 | | | 60-48-18 | -60+32+0 | -180+144+27 | | | -28+36-6 | 28-24+0 | 84-108+9 | |
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= | | -16×2+8×-3+12×2 | -16×-2+8×2+12×0 | -16×-6+8×9+12×-3 | | | -6×2-28×-3-9×2 | -6×-2-28×2-9×0 | -6×-6-28×9-9×-3 | | | 2×2+4×-3-15×2 | 2×-2+4×2-15×0 | 2×-6+4×9-15×-3 | |
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= | | -32-24+24 | 32+16+0 | 96+72-36 | | | -12+84-18 | 12-56+0 | 36-252+27 | | | 4-12-30 | -4+8+0 | -12+36+45 | |
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= | | -32×2+48×-3+132×2 | -32×-2+48×2+132×0 | -32×-6+48×9+132×-3 | | | 54×2-44×-3-189×2 | 54×-2-44×2-189×0 | 54×-6-44×9-189×-3 | | | -38×2+4×-3+69×2 | -38×-2+4×2+69×0 | -38×-6+4×9+69×-3 | |
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= | | -64-144+264 | 64+96+0 | 192+432-396 | | | 108+132-378 | -108-88+0 | -324-396+567 | | | -76-12+138 | 76+8+0 | 228+36-207 | |
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= | | 56 | 160 | 228 | | | -138 | -196 | -153 | | | 50 | 84 | 57 | |
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(A7)×A | = | | 56 | 160 | 228 | | | -138 | -196 | -153 | | | 50 | 84 | 57 | |
| × | |
= | | 56×2+160×-3+228×2 | 56×-2+160×2+228×0 | 56×-6+160×9+228×-3 | | | -138×2-196×-3-153×2 | -138×-2-196×2-153×0 | -138×-6-196×9-153×-3 | | | 50×2+84×-3+57×2 | 50×-2+84×2+57×0 | 50×-6+84×9+57×-3 | |
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= | | 112-480+456 | -112+320+0 | -336+1440-684 | | | -276+588-306 | 276-392+0 | 828-1764+459 | | | 100-252+114 | -100+168+0 | -300+756-171 | |
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= | | 88 | 208 | 420 | | | 6 | -116 | -477 | | | -38 | 68 | 285 | |
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(A8)×A | = | | 88 | 208 | 420 | | | 6 | -116 | -477 | | | -38 | 68 | 285 | |
| × | |
= | | 88×2+208×-3+420×2 | 88×-2+208×2+420×0 | 88×-6+208×9+420×-3 | | | 6×2-116×-3-477×2 | 6×-2-116×2-477×0 | 6×-6-116×9-477×-3 | | | -38×2+68×-3+285×2 | -38×-2+68×2+285×0 | -38×-6+68×9+285×-3 | |
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= | | 176-624+840 | -176+416+0 | -528+1872-1260 | | | 12+348-954 | -12-232+0 | -36-1044+1431 | | | -76-204+570 | 76+136+0 | 228+612-855 | |
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= | | 392 | 240 | 84 | | | -594 | -244 | 351 | | | 290 | 212 | -15 | |
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A is not a periodic matrix
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