Kev sib xyaw ua ke yog ib txoj hauv kev los suav tag nrho cov txiaj ntsig ntawm qhov xwm txheej uas qhov kev txiav txim ntawm qhov tshwm sim tsis muaj teeb meem. Txhawm rau xam cov kev sib txuas, peb yuav siv qhov formula nCr=n! /r yog!(n - r)!, qhov twg n sawv cev rau tag nrho cov khoom, thiab r sawv cev rau cov khoom raug xaiv ib zaug.
Muaj pes tsawg qhov sib xyaw ntawm 4 yam khoom muaj?
I.e. muaj 4 yam khoom, yog li tag nrho cov kev sib txuas ua ke uas lawv tuaj yeem npaj tau yog 4!=4 x 3 x 2 x 1=24.
Puas muaj cov qauv rau kev sib txuas?
Cov qauv sib xyaw ua ke yog: nCr=n! / ((n – r)! r!) n=tus naj npawb ntawm cov khoom.
nPr formula yog dab tsi?
Permutation: nPr sawv cev rau qhov tshwm sim ntawm kev xaiv cov khoom xaj ntawm 'r' los ntawm ib pawg ntawm 'n' cov khoom. Qhov kev txiav txim ntawm cov khoom tseem ceeb nyob rau hauv cov ntaub ntawv ntawm permutation. Tus qauv los nrhiav nPr yog muab los ntawm: nPr=n!/(n-r)! … nCr=n!/[r!
NCN formula yog dab tsi?
Ua tiav cov lus teb ib ntus:
nCr=n! r kev! (n−r)! Ntawm no, n sawv cev rau tus naj npawb ntawm cov khoom, thiab r sawv cev rau tus naj npawb ntawm cov khoom raug xaiv ib zaug.
