tolong dijawab kk beserta caranya

Kombinasi

2.
(n+1) C5  = n C4
(n+1) !/ (n+1-5)! . 5!  = n! / (n-4)!. 4!
(n+1)!/ (n-4)! .5! = n! /(n-4)!. 5!
(n+1)!/ (n) !  =  (n-4)!. 5!/ (n-4)! . 4!
(n+1). n! / n!  = 5.4!/4!
n + 1 = 5
n = 4

4.
banyak soal = 10
harus dijawab = 7
wajib dijawab  = 3


banyak pilihan = (10-3) C (7-3) = 7 C4
= 7 !/ (7-4)! . 4!
= 7!/ 3!. 4!
= (7.6. 5.4!) / (4!). 3.2
= (7.6.5)/(3.2)
= 7.5
= 35