Răspuns:
Explicație pas cu pas:
a) 1/1*2 = 1/1 -1/2, 1/2*3 = 1/2 - 1/3...
Suma = 1 -1/2 +1/2 -1/3+1/3 -1/4...1/99 -1/100=
1 - 1/100 = 99/100
1/2 < 99/100 < 1 evident
b) 2/1*3 = 1/1 - 1/3, 2/3*5 = 1/3 -1/5, ...
Suma = 1 - 1/101 = 100/101
2/5 < 100/101 < 1 evident
