Ôn tập toán 7
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2 tháng 1 2017 lúc 14:54
Cho và
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Tính :
\(D=\frac{\left(\frac{3}{10}-\frac{4}{5}-\frac{7}{20}\right).\frac{-5}{19}}{\left(\frac{1}{14}+\frac{1}{7}-\frac{-3}{35}\right).\frac{4}{3}}\)
\(E=\frac{1-\frac{1}{3}+\frac{1}{1+\frac{1}{3}}}{1-\frac{1}{3}-\frac{1}{1\frac{1}{3}}}\)
\(G=1-\frac{1}{1-\frac{2}{1-\frac{3}{1-\frac{1}{4}}}}\)
CMR : E = \(1-\frac{1}{2^2}-\frac{1}{3^2}-...-\frac{1}{2004^2}>\frac{1}{2004}\)
F = \(\frac{1}{2^2}+\frac{1}{4^2}+...+\frac{1}{200^2}< \frac{1}{2}\)
H = \(\frac{1}{3}+\frac{2}{3^2}+\frac{3}{3^3}+...+\frac{100}{3^{100}}< \frac{3}{4}\)
\(\frac{\frac{2000}{11}+\frac{2000}{12}+...+\frac{2000}{100}}{\frac{1}{99}+\frac{2}{98}+\frac{3}{97}+...+\frac{98}{2}+\frac{99}{1}}\)
Hãy rút gọn
\(\left(\frac{3}{5}+0,415-\frac{3}{200}\right).2\frac{2}{3}.0,25\)
Tính
B=1-\(\frac{1}{2}\)(1+2)-\(\frac{1}{3}\)(1+2+3)-\(\frac{1}{4}\)(1+2+3+4)-...-\(\frac{1}{20}\)(1+2+3+...+20)
\(\frac{\left(\frac{3}{10}-\frac{4}{15}-\frac{7}{20}\right).\frac{5}{19}}{\left(\frac{1}{14}+\frac{1}{7}-\frac{-3}{35}\right).\frac{-4}{3}}=???\)
Tìm x biết :
a) \(-\frac{2}{3}.x+4=-12\)
b) \(-\frac{3}{4}+\frac{1}{4}:x=-3\)
c) \(\frac{x+1}{2}+\frac{x+2}{3}+\frac{x+1}{4}=\frac{x+1}{5}+\frac{x+1}{6}\)
d)\(\frac{x+1}{2009}+\frac{x+2}{2008}+\frac{x+3}{2007}=\frac{x+10}{2000}+\frac{x+11}{1999}+\frac{x+12}{1998}\)
A=\(\frac{\frac{2}{39}-\frac{1}{15}-\frac{2}{153}}{\frac{1}{34}+\frac{3}{20}-\frac{3}{26}}:\frac{1+\frac{2}{71}-\frac{5}{121}}{\frac{65}{121}-\frac{26}{71}-13}\)