Question

Considerando que Cn,3= 2Cn,2, o valor de n é de?

Answer 1

n!/(n-3)!3!=2.[n!/(n-2)!2!]

= (n-1).(n-2).(n-3)!/(n-3)!3!=2.[(n-1).(n-2)/(n-2)!2!]


=(n-1).(n-2)/6=2.[(n-1)/2]

n^2-3n+2/6=(n-1)

n^2-3n+2=6n-6

n^2-3n-6n+2+6=0

n^2-9n+8=0

∆=b^2-4.a.c

∆=(-9)^2-4.1.(8)

∆=81-32

∆=49

n1=-b+√∆/2.a

n1=-(-9)+√49/2.1

n1=9+7/2

n1=16/2

n1=8

n2=-b-√∆/2.a

n2=-(-9)+√49/2.1

n2=9-7/2

n2=2/2

n2=1


s={1;8}

espero ter ajudado!

bom dia !