8D= 1.3.5.8 - 3.5.7.8 + 5.7.9.8 - ... + 97.99.101.8
8D=1.3.5.(7+1)-3.5.7.(9-1)+5.7.9.(11-3) - ... + 97.99.101.(103-95)
8D=1.3.5.7+3.5-3.5.7.9-1.3.5.7+5.7.9.11-3.5.7.9-...+97.99.101.103-95.97.99.101
8D=3.5+97.99.101.103=99900024
D=12487503
\(A=\frac{2}{1\cdot3\cdot5}\cdot\frac{2}{5\cdot7\cdot9}\cdot...\cdot\frac{2}{97\cdot99\cdot101}\)
tính
Tính : \(E=1\cdot3^3+3\cdot5^3+5\cdot7^3+...+97\cdot99^3\)
a)A=\(\frac{1}{1\cdot3\cdot5}+\frac{1}{3\cdot5\cdot7}+\frac{1}{5\cdot7\cdot9}+...+\frac{1}{25\cdot27\cdot29}\)
b)\(\left(\frac{1}{1\cdot101}+\frac{1}{2\cdot102}+...+\frac{1}{10\cdot110}\right)\cdot x=\frac{1}{1.11}+\frac{1}{2\cdot12}+...+\frac{1}{100\cdot110}\)
\(A=\frac{1}{2\cdot3}+\frac{1}{6\cdot5}+\frac{1}{10\cdot7}+\frac{1}{14\cdot9}+....+\frac{1}{198\cdot101}\)
Tính tổng
A=\(\frac{2}{3\cdot5}+\frac{2}{5\cdot7}+\frac{2}{7\cdot9}+...+\frac{2}{97\cdot99}\)
Tính S=\(\frac{2}{1\cdot3}\)-\(\frac{4}{3\cdot5}\)+\(\frac{6}{5\cdot7}\)-\(\frac{8}{7\cdot9}\)+...-\(\frac{96}{95\cdot97}\)+\(\frac{98}{97\cdot99}\)
Cho \(U_1=\frac{1}{1\cdot3\cdot5}\); \(U_2=\frac{1}{1\cdot3\cdot5}+\frac{1}{3\cdot5\cdot7}\); \(U_3=\frac{1}{1\cdot3\cdot5}+\frac{1}{3\cdot5\cdot7}+\frac{1}{5\cdot7\cdot9}\)
a) Lập quy trình tổng quát tính Un
b) Tính U50, U60
c) Tính U1002
\(1\frac{1}{3\cdot5}+\frac{4}{5\cdot7}+\frac{1}{7\cdot9}+...+\frac{1}{99\cdot101}\)
95*.Tính nhanh
\(\frac{2}{3\cdot5}+\frac{2}{5\cdot7}+\frac{2}{7\cdot9}+...+\frac{2}{97\cdot99}\)