Ob pawg A thiab B muaj tib daim cardinality yog tias muajib qho kev sib tham (k.k.a., ib-rau-ib tsab ntawv) los ntawm A mus rau B, uas yog, muaj nuj nqi los ntawm A mus rau B uas yog ob qho tib si txhaj tshuaj thiab ua tiav. Cov txheej txheem zoo li no tau hais tias yog sib npaug, sib npaug, lossis sib npaug.
Puas cov teev N thiab Z muaj tib daim cardinality?
1, the sets N thiab Z muaj tib yam cardinality. Tej zaum qhov no tsis yog qhov xav tsis thoob, vim tias N thiab Z muaj qhov muaj zog geometric zoo ib yam li cov ntsiab lus ntawm kab zauv. Dab tsi yog qhov xav tsis thoob yog tias N (thiab yog li Z) muaj tib lub cardinality raws li lub teeb Q ntawm txhua tus lej rational.
Do 0 1 thiab 0 1 muaj tib daim cardinality?
Qhia tias lub sijhawm qhib (0, 1) thiab lub sijhawm kaw [0, 1] muaj tib lub cardinality. Qhov qhib ncua sij hawm 0 <x< 1 yog ib qho subset ntawm lub sijhawm kaw 0 ≤ x ≤ 1. Hauv qhov xwm txheej no, muaj qhov "pom meej" kev ua haujlwm f: (0, 1) → [0, 1], uas yog lub luag haujlwm f(x)=x ∈ (0, 1).
Cardinality piv txwv yog dab tsi?
Lub cardinality ntawm ib lub teeb yog ntsuas ntawm lub teeb qhov loj, lub ntsiab lus ntawm cov ntsiab lus hauv cov teeb. Piv txwv li, lub teeb A={ 1, 2, 4 } A=\{1, 2, 4} A={1, 2, 4} muaj ib tug cardinality ntawm 3 rau peb lub ntsiab lus uas muaj nyob rau hauv nws.
Puas tau ib lub subset muaj tib lub cardinality?
Ib qho tsis kawg thiab ib qho ntawm nws cov subsets tsim nyog tuaj yeem muaj tib daim cardinality. Ib qho piv txwv: Cov kab zauv Z thiabnws cov subset, txheej ntawm tus lej E={… … Yog li, txawm tias E⊂Z, |E|=|Z|.
