Muaj txoj haujlwm txhaj tshuaj B → A, tab sis tsis muaj kev txhaj tshuaj A → B. Yog li yog tias peb siv qhov ntawd raws li peb lub ntsiab lus, lub hauv paus ntsiab lus pigeonhole yog tsis yogyog qhov pov thawj - hloov nws yog ib feem ntawm lub ntsiab lus ntawm qhov nws txhais tau li cas rau ib lub teeb kom loj dua lwm qhov..
Yuav ua li cas koj ua pov thawj txoj cai pigeonhole?
(Txoj Cai Pigeonhole, yooj yim version.) Yog tias k+1 lossis ntau dua pigeons raug faib rau k pigeonholes, ces tsawg kawg ib pigeonhole muaj ob lossis ntau dua pigeons Pov thawj. Lub contrapositive ntawm nqe lus yog: Yog hais tias txhua tus pigeonhole muaj nyob rau hauv feem ntau ib tug nquab, ces muaj nyob rau hauv feem ntau k pigeons.
Vim li cas peb thiaj xav tau txoj ntsiab cai pigeonhole?
Yog muaj ib tug neeg tuaj yeem tuav tes nrog ib leeg (qhov twg n > 1), txoj ntsiab cai nquab qhia tau hais tias tseem muaj ib khub neeg yuav tuav tes nrog tus lej ntawm tib neeg Hauv daim ntawv thov ntawm lub hauv paus ntsiab lus no, 'lub qhov' uas tus neeg raug muab yog tus lej ntawm tes tuav tus neeg ntawd.
Ua raws li tau qhia Kuv hais lub hauv paus ntsiab lus nquab?
Qhov no qhia txog lub hauv paus ntsiab lus dav dav hu ua txoj cai pigeonhole, uas hais tias yog tias muaj pigeons ntau dua pigeonholes, ces yuav tsum muaj tsawg kawg yog ib tug nquab nrog tsawg kawg yog ob pigeons nyob rau hauv.
Puas yog tus nquab qhov hauv paus ntsiab lus yog axiom?
Txoj ntsiab cai nquab yog a axiom ntawm lej- ematics, hais tias tsis muaj ib-rau-ib daim phiaj los ntawm m pigeons mus rau n qhov, m > n. Nws qhia txog qhov tseeb tseem ceeb heev txog cardinalities ntawm cov teev thiab yog siv ubiquitously nyob rau hauv yuav luag txhua qhov chaw ntawm kev ua lej.
