Răspuns:
Explicație pas cu pas:
a)
1/10 + 3/10 + 5/10 + .... + 19/10 = (1 + 3 + 5 + ....+19)/10 = 100/10 = 10
1 + 3 + 5 + ....+19 = 10*(1 + 19)/2 = 10*20/2 = 100
b)
2 - 3/2 = 4/2 - 3/2 = 1/2
2 - 4/3 = 6/3 - 4/3 = 2/3
2 - 5/4 = 8/4 - 5/4 = 3/4
2 - 6/5 = 10/5 - 6/5 = 4/5
.....
2 - 19/18 = 36/2 - 19/18 = 17/18
2 - 20/19 = 38/19 - 20/19 = 18/19
Produsul devine
1/2*2/3*3/4*4/5*....*17/18*18/19 = 1/19
