ta có
1/n.1/n+1=1/n(n+1)
1/n-1/n+1=n+1-n/n(n+1)=1/n(n+1)
=>1/n.1/n+1=1/n-1/n+1
1/n.1/n+1=1/n(n+1);1/n-1/n+1
=n+1-n(n+1)
=>1/n.1/n+1=1/n-1/n+1
Vậy đã CMR rồi nha !!!
CMR1×2-1/2!+2×3-1/2!+3×4-1/4!+...+2023×2024/2024!<2
CMR1/10^2+1/15^2+...+1/500^2<1/15
CMR1+1+1+1+1+1+.....+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1++1+1
là hợp số
chứng minh rằng
1, 1/n(n+1)=1/n-1/n+1
2, 2/n(n+1)(n+2)=1/n(n+1)-1/(n+1)(n+2)
3, 3/n(n+1)(n+2)(n+3)=1/n(n+1)(n+2)-1/(n+1)(n+2)(n+3)
4, 4/(2n-1)(2n+1)(2n+3)=1/(2n+1)(2n-1)-1/(2n+1)(2n+3)
5, m/n(n+m)=1/n-1/n+m
6, 2m/n(n+m)(n+2n)=1/n(n+m)-1/(n+m)(n+2n)
cho tong S =4/3+1/4+1/5+...+1/8+1/9
CMR1 <S<2 chu y / la phan so
chứng minh rằng
1, 1/n(n+1)=1/n-1/n+1
2, 2/n(n+1)(n+2)=1/n(n+1)-1/(n+1)(n+2)
3, 3/n(n+1)(n+2)(n+3)=1/n(n+1)(n+2)-1/(n+1)(n+2)(n+3)
4, 4/(2n-1)(2n+1)(2n+3)=1/(2n+1)(2n-1)-1/(2n+1)(2n+3)
5, m/n(n+m)=1/n-1/n+m
6, 2m/n(n+m)(n+2n)=1/n(n+m)-1/(n+m)(n+2n)
ai nhanh mình tick trước 9 giờ
chứng minh : 1/ n (n+1) (n+2) = 1/ 2 ( 1/ n(n+1) - 1/(n+1 ) (n+2) )
Chọn câu trả lời đúng : 1.2 + 2.3 + 3.4 + ... + (n - 1)n + n(n + 1) =
A n(n+1)(2n+1)4+n(n+1)2
B n(n+1)(2n+1)6+n(n−1)2
C n(n+1)(2n+1)6+n(n+1)2
D n(n+2)(2n+1)6+n(n+1)2
Cho n thuộc N sao hãy chứng tỏ :
1/n(n+1)(n+2)=1/2[1/n(n+1)-1/(n+1)(n+2)]
cho hai phan so 1/n và 1/n+1 vói n thuoc Z và n khac 0 chung to 1/n.1/n+1=1/n-1/n+1
