1. is Periodic Matrix ?
`[[1,-2,-6],[-3,2,9],[2,0,-3]]`
Solution:
A square matrix `A` is called a periodic matrix, if `A^m = A` for some positive integer m.
`A` | = | | `1` | `-2` | `-6` | | | `-3` | `2` | `9` | | | `2` | `0` | `-3` | |
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`A×A` | = | | `1` | `-2` | `-6` | | | `-3` | `2` | `9` | | | `2` | `0` | `-3` | |
| × | | `1` | `-2` | `-6` | | | `-3` | `2` | `9` | | | `2` | `0` | `-3` | |
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= | | `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` | `-6` | `-6` | | | `9` | `10` | `9` | | | `-4` | `-4` | `-3` | |
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`(A^2)×A` | = | | `-5` | `-6` | `-6` | | | `9` | `10` | `9` | | | `-4` | `-4` | `-3` | |
| × | | `1` | `-2` | `-6` | | | `-3` | `2` | `9` | | | `2` | `0` | `-3` | |
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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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= | | `1` | `-2` | `-6` | | | `-3` | `2` | `9` | | | `2` | `0` | `-3` | |
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Here `A^3 = A`, so `A` is a periodic matrix of period 2
2. is Periodic Matrix ?
`[[2,-2,-6],[-3,2,9],[2,0,-3]]`
Solution:
A square matrix `A` is called a periodic matrix, if `A^m = A` for some positive integer m.
`A` | = | | `2` | `-2` | `-6` | | | `-3` | `2` | `9` | | | `2` | `0` | `-3` | |
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`A×A` | = | | `2` | `-2` | `-6` | | | `-3` | `2` | `9` | | | `2` | `0` | `-3` | |
| × | | `2` | `-2` | `-6` | | | `-3` | `2` | `9` | | | `2` | `0` | `-3` | |
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= | | `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` | `-8` | `-12` | | | `6` | `10` | `9` | | | `-2` | `-4` | `-3` | |
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`(A^2)×A` | = | | `-2` | `-8` | `-12` | | | `6` | `10` | `9` | | | `-2` | `-4` | `-3` | |
| × | | `2` | `-2` | `-6` | | | `-3` | `2` | `9` | | | `2` | `0` | `-3` | |
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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` | `-12` | `-24` | | | `0` | `8` | `27` | | | `2` | `-4` | `-15` | |
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`(A^3)×A` | = | | `-4` | `-12` | `-24` | | | `0` | `8` | `27` | | | `2` | `-4` | `-15` | |
| × | | `2` | `-2` | `-6` | | | `-3` | `2` | `9` | | | `2` | `0` | `-3` | |
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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` | `-16` | `-12` | | | `30` | `16` | `-9` | | | `-14` | `-12` | `-3` | |
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`(A^4)×A` | = | | `-20` | `-16` | `-12` | | | `30` | `16` | `-9` | | | `-14` | `-12` | `-3` | |
| × | | `2` | `-2` | `-6` | | | `-3` | `2` | `9` | | | `2` | `0` | `-3` | |
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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` | `8` | `12` | | | `-6` | `-28` | `-9` | | | `2` | `4` | `-15` | |
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`(A^5)×A` | = | | `-16` | `8` | `12` | | | `-6` | `-28` | `-9` | | | `2` | `4` | `-15` | |
| × | | `2` | `-2` | `-6` | | | `-3` | `2` | `9` | | | `2` | `0` | `-3` | |
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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` | `48` | `132` | | | `54` | `-44` | `-189` | | | `-38` | `4` | `69` | |
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`(A^6)×A` | = | | `-32` | `48` | `132` | | | `54` | `-44` | `-189` | | | `-38` | `4` | `69` | |
| × | | `2` | `-2` | `-6` | | | `-3` | `2` | `9` | | | `2` | `0` | `-3` | |
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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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`(A^7)×A` | = | | `56` | `160` | `228` | | | `-138` | `-196` | `-153` | | | `50` | `84` | `57` | |
| × | | `2` | `-2` | `-6` | | | `-3` | `2` | `9` | | | `2` | `0` | `-3` | |
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= | | `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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`(A^8)×A` | = | | `88` | `208` | `420` | | | `6` | `-116` | `-477` | | | `-38` | `68` | `285` | |
| × | | `2` | `-2` | `-6` | | | `-3` | `2` | `9` | | | `2` | `0` | `-3` | |
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= | | `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
This material is intended as a summary. Use your textbook for detail explanation.
Any bug, improvement, feedback then