Ta có:
\(P=\dfrac{2}{1\cdot3}+\dfrac{2}{3\cdot5}+...+\dfrac{2}{99\cdot101}\)
\(P=1-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{5}+...+\dfrac{1}{99}-\dfrac{1}{101}\)
\(P=1-\left(\dfrac{1}{3}-\dfrac{1}{3}\right)-\left(\dfrac{1}{5}-\dfrac{1}{5}\right)-...-\left(\dfrac{1}{99}+\dfrac{1}{99}\right)-\dfrac{1}{101}\)
\(P=1-0-0-...-0-\dfrac{1}{101}\)
\(P=1-\dfrac{1}{101}< 1\)
Tinh 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
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 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) 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
c) 4/2.4+4/4.6+4/6.8+...+4/2008.2010
2/1.3+2/3.5+2/5.7+......2/99.101
2/1.3+2/3.5+2/5.7+.....+2/99.101 = ?
2/1.3+2/3.5+2/5.7+...+2/99.101
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
Tính : A=2/1.3+2/3.5+2/5.7+...+2/99.101 =?
Tính tổng:
a,\(\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{99.101}\)
b,\(\frac{5}{1.3}+\frac{5}{3.5}+\frac{5}{5.7}+...+\frac{5}{99.101}\)
