A=1/4+1/3+1/5+1/3+..............+1/3+1/17=19.1/3+(1/5+1/6+..........+1/17)
1/4+1/5+..............+1/17=(1/4+1/17)x19/2=(21.19)/(8.17)
A=19/3.(21.19)/(8.17)=(19².7)/(8.17)
desfacem fractiile si obtinem
B=1/3-1/4+1/3-1/5+1/3-1/6+............+1/3-1/17=14/3-(1/4+1/5+...........+1/17)=14/3-
(1/4+1/17).14/2=(21.17)/(14.2)=(3.17)/4
A+B=19².7.3.17/4.8.17=7581/32
Am folosit la sume formula
S=(a1+an).n/2
unde a1=primul termen al sumei
an- ultimul termen
n- numarul de termeni
te rog sa verifici
