\(\left(\frac{1}{1.3}+\frac{1}{3.5}+...+\frac{1}{99.101}\right)-X=2\)
\(\frac{1}{2}.\left(\frac{2}{1.3}+\frac{2}{3.5}+...+\frac{2}{99.101}\right)-X=2\)
\(\frac{1}{2}.\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{99}-\frac{1}{101}\right)-X=2\)
\(\frac{1}{2}.\left(1-\frac{1}{101}\right)-X=2\)
\(\frac{1}{2}.\frac{100}{101}-X=2\)
\(\frac{50}{101}-X=2\)
\(X=\frac{50}{101}-2\)
\(X=\frac{-152}{101}\)
Bài 1: Tính tổng
a, 2\1.3+2\3.5+2\5.7+.......+2\99.101
b, 5\1.3+5\3.5+5\5.7+......+5\99.101
Bài 2: CMR phân số 2n+1\3n+2 là phân số tối giản
Tính tổng
a. 1/1.2 + 1/2.3 + 1/3.4 + ...+ 1/2015.2016
b. 2/1.3 + 2/3.5 + 2/5.7 + ...+ 2/99.101
c. 5/1.3 + 5/3.5 + 5/5.7 + ...+ 5/99.101
d. 1/2 + 1/6 + 1/12 + 1/20 + ...+ 1/9900
bn nào trả lời nhanh mik tích, cảm ơn ạ
A = 1/1.3 - 1/3.5 - 1/5.7 - ... - 1/99.101
1/1.3+1/3.5+1/5.7+.........+1/99.101
a)1+1/1.3+1/3.5+...+1/99.101
b)1/2+1/2.5+1/5.8+1/8.11+...+1/98.101
Tính 1/1.3+1/3.5+1/5.7+...1/99.101
(1+1/1.3).(1+1/2.4)(1+1/3.5)....(1+1/99.101)
(1+1/1.3).(1+1/2.4).(1+1/3.5).........(1+1/99.101)
(1+1/1.3)(1+1/2.4)(1+1/3.5)...(1/1+1/99.101)
