F=(3/1.8+3/8.15+...+3/106.113)-(25/50.55+25/55.60+...+25/95.100) (1)
Đặt:
A=(3/1.8+3/8.15+3/15.22+...+3/106.113)
=3/7.(1-1/8+1/8-1/15+...+1/106-1/113)
=3/7.(1-1/113)
=3/7.112/113
=336/791. (2)
B=25/50.55+25/55.60+...+25/95.100
=25/5.(1/50-1/55+1/55-1/60+...+1/95-1/100)
=5.(1/50-1/100)
=1/20 (3)
Thay (2),(3) vào (1) ta được:
F=336/791-1/20
=5929/6720.
1.
a) \(\text{(3x-5)6=(3x-5)4}\)
2.
a)\(\frac{2}{7}.\frac{2012}{2011}-\frac{2}{2011}.\frac{1}{7}_{ }+\frac{4}{7}\)
b) \(\left(\frac{3}{1.8}+\frac{3}{8.15}+\frac{3}{15.22}+...+\frac{3}{106.113}\right)-\left(\frac{25}{50,55}\frac{25}{55.60}\frac{25}{60.65}...\frac{25}{95.100}\right)\)
ai nhanh đúng mk tk
Bài 1: Tính tổng: \(S=\frac{3}{2\cdot3}+\frac{3}{3\cdot6}+\frac{3}{4\cdot9}+...+\frac{3}{6039\cdot2014}\)
Bài 2: Rút gọn phân số: \(S=\frac{25^{28}+25^{24}+...+25^4+1}{25^{30}+25^{28}+...+25^2+1}\)
Tính nhanh : \(\frac{\frac{2}{33}+\frac{2}{25}+\frac{2}{19}}{\frac{3}{33}+\frac{3}{25}+\frac{3}{19}}\)
Bài 1: Tính tổng:\(S=\frac{3}{2\cdot3}+\frac{3}{3\cdot6}+\frac{3}{4\cdot9}+\frac{3}{2014\cdot6039}\)
Bài 2: Rút gọn phân số: \(S=\frac{25^{28}+25^{24}+...+25^4+1}{25^{30}+25^{28}+...+25^2+1}\)
\(\frac{4}{25}.\frac{5}{9}+\frac{-4}{25}.\frac{10}{3}+5\frac{7}{9}\)
\(\frac{9}{25}x+\frac{3}{5}\left(\frac{9}{25}x+18\right)+\frac{9}{25}x+18=x\)
A = \(26:[\frac{(3:10,2-0,1)}{25.\left(0,8+1,2\right)}+\frac{\left(34,06-33,81\right).4}{6,84:\left(38,57-25,15\right)}]+\frac{2}{3}:\frac{4}{21}\)
B = \(\frac{0,8:\left(\frac{4}{5}.1,25\right)}{0,64-\frac{1}{25}}+\frac{\left(1,08-\frac{2}{25}\right):\frac{4}{7}}{(6\frac{5}{9}-3\frac{1}{4}).2\frac{2}{17}}+\left(1,2.0,5\right)\)
\(\frac{0,8:\left(\frac{4}{5}.1,25\right)}{0,64-\frac{1}{25}}+\frac{\left(100-\frac{2}{25}\right):\frac{4}{7}}{\left(6\frac{5}{9}-3\frac{1}{4}\right).2\frac{2}{27}}+\left(1,2.0,5\right):\frac{3}{5}\)
C=\(\frac{49}{1.8}\)+ \(\frac{49}{8.15}\)+ \(\frac{49}{15.22}\)+ ... + \(\frac{49}{141.148}\)
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