Question

Ex.27 ajutati-ma va rog
Dau coronita

Answer 1

Aplicam 1+2+...+n=n(n+1)/2

a)
(14*15)/2=7*15=105
(6*7)/2=3*7=21
105/21=5

b)
(1*2*3*...*15)/((15*16)/2)=(1*2*3*...*15)*2/(15*16)=1*2*3*4*5*6*7*9*10*11*12*13*14