Va rog!Dau coroana si 15 puncte.

Răspuns:
a = 1-1/2+1/2-1/4+1/4-1/8+...+1/2^98 -
- 1/2^99 + 1/2^99-1/2^100=
= 1-1/2^100 = (2^101 - 2)/2^101;
b = 1/4 - 1/2^101 =
= (2^99 - 1)/2^101
=> b < a;
(a - b) = (3*2^99 - 1)/2^101;
3*2^99 - 1 < 2^101 = 4*2^99;
Ca urmare (a - b) < 3/2.