so sanh (a+1).(a+2).(a+3)-a.(a+1).(a+2) va 3(a+1).(a+2)
b,tinh
M=1.2+2.3+3.4+...+ 2002.2003
GIUP MINH NHANH LEN NHE CAC BAN!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
1/1.2+1/2.3+1/3.4+...+1/x(x+1)=2/3
a, 1/1.2 + 1/2.3 + 1/3.4 + ... + 1/ x. (x + 1) = 201
1/1.2+1/2.3+1/3.4+...+1/x.(x+1)=2015/2016
1/1.2+1/2.3+1/3.4+...+1/x.(x+1)=19/20
1.2 + 2.3 + 3.4+...+ ( n - 1 ) .n
giup mk cau nay nhe
(1/1.2 +1/2.3 1/3.4 + ....+1/8.9) x=23/45
(1/1.2 +1/2.3 1/3.4 + ....+1/8.9) x=23/45
Tìm x, biết
1/1.2+1/2.3+1/3.4+...........+1/x.(x+1)= 2017/2018
