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Tunjukkan bahwa C ( 10 , 2 ) = C ( 10 , 8 ) = 2 ! P ( 10 , 2 ) ​ .

Tunjukkan bahwa .

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E. Safitri

Master Teacher

Jawaban terverifikasi

Jawaban

terbukti bahwa C ( 10 , 2 ) = C ( 10 , 8 ) = 2 ! P ( 10 , 2 ) ​ .

terbukti bahwa .

Pembahasan

Kombinasi dan permutasi pada soal di atas dapat dihitung dengan rumus berikut: n ​ C r ​ = ( n − r )! ⋅ r ! n ! ​ n ​ P r ​ = ( n − r )! n ! ​ Didapat n ​ P 2 ​ = 90 sehingga 2 ! P ( 10 , 2 ) ​ = 2 ⋅ 1 10 ​ P 2 ​ ​ = 2 90 ​ = 45 . Dengan demikian, terbukti bahwa C ( 10 , 2 ) = C ( 10 , 8 ) = 2 ! P ( 10 , 2 ) ​ .

Kombinasi dan permutasi pada soal di atas dapat dihitung dengan rumus berikut:

 

table attributes columnalign right center left columnspacing 0px end attributes row cell C presubscript 10 subscript 2 end cell equals cell fraction numerator 10 factorial over denominator left parenthesis 10 minus 2 right parenthesis factorial times 2 factorial end fraction end cell row blank equals cell fraction numerator 10 factorial over denominator 8 factorial times 2 factorial end fraction end cell row blank equals cell fraction numerator 10 times 9 times up diagonal strike 8 factorial end strike over denominator up diagonal strike 8 factorial end strike times 2 times 1 end fraction end cell row blank equals cell 90 over 2 end cell row blank equals 45 end table

table attributes columnalign right center left columnspacing 0px end attributes row cell C presubscript 10 subscript 8 end cell equals cell fraction numerator 10 factorial over denominator left parenthesis 10 minus 8 right parenthesis factorial times 8 factorial end fraction end cell row blank equals cell fraction numerator 10 factorial over denominator 2 factorial times 8 factorial end fraction end cell row blank equals cell fraction numerator 10 times 9 times up diagonal strike 8 factorial end strike over denominator 2 times 1 times up diagonal strike 8 factorial end strike end fraction end cell row blank equals cell 90 over 2 end cell row blank equals 45 end table

 

table attributes columnalign right center left columnspacing 0px end attributes row cell P presubscript n subscript 2 end cell equals cell fraction numerator 10 factorial over denominator left parenthesis 10 minus 2 right parenthesis factorial end fraction end cell row blank equals cell fraction numerator 10 factorial over denominator 8 factorial end fraction end cell row blank equals cell fraction numerator 10 times 9 times up diagonal strike 8 factorial end strike over denominator up diagonal strike 8 factorial end strike end fraction end cell row blank equals 90 end table

Didapat  sehingga .

Dengan demikian, terbukti bahwa .

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