Răspuns:
a= 1+5/2+10/3+17/4+...+100/99=
(1+4/2+1/2)+(9/3+1/3)+(16/4+1/4)=
a=(1+2+3+4+....+99)+(1/2+1/3+1/4+...+1/99)
b=1/2+2/3+.+98/99=(2-1)/2+(3-1)/3+.+(99-1)/99
1-1/2+1-1/3+1-1/4+..+1-1/99=
b=98-(1/2+1/3+1/4+...+1/99)
a+b=(1+2+3+...99)+(1/2+1/3+.. 1/99)-
98-(1/2+1/3+.. +1/99)=
1+2+3+4+...+99+98=99×100/2+98=
4950+98=5048
suma= n(n+1)/2
