Răspuns:
a=2/1×3 + 2/3×5 + ... + 2/49×51
a= 2/1-2/3 + 2/3-2/5 + ... + 2/49-2/51 (reducem)
a=2/1-2/51 (dam numitor comun pe 51)
a=102-2/51
a=100/51
a=1.96...
=> a apartine (1/2,1)
/=bara fractie
