Verified answer

=(1-1/2)+(1/2-1/3)+...+(1/9-1/10)

=1-1/10

=9/10

S = (1 - 1/2) + (1/2 - 1/3) + ( 1/3 - 1/4) + ....+ (1/9 - 1/10)

= 1 - 1/10

= 9/10 . ( em mới học lớp 3 đúng ko?)

Phan tich

1/1.2=(2-1)/1.2=1-1/2

1/2.3=(3-2)/2.3=1/2-1/3

1/3.4=(4-3)/3.4=1/3-1/4

......

1/9.10=(10-9)/9.10=1/9-1/10

triet tieu nhau

con lai la 1-1/10=9/10

nho binh chon cau tra loi thu vi nha.hj

S= 1/1.2 + 1/2.3+ 1/ 3.4 ..... + 1/9.10

S=1/1-1/2+1/2-1/3+1/3-1/4+....+1/9-1/10

S=1/1-1/10

S=9/10