\(\frac{\text{1984.1985 + 1986.20 + 1965}}{1985.200-1984.1986}=-1,123249617\approx-1,13\)
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Rút gọn
1. \(\frac{5}{9}.\frac{7}{13}+\frac{5}{9}.\frac{9}{13}-\frac{5}{9}.\frac{3}{13}\)
2. \(\left(\frac{1+\frac{1}{5}+\frac{1}{7}+\frac{1}{11}}{2+\frac{2}{5}+\frac{2}{7}+\frac{2}{17}}:\frac{4-\frac{4}{7}+\frac{4}{9}-\frac{4}{13}}{1-\frac{1}{7}+\frac{1}{9}-\frac{1}{13}}\right):\frac{838383}{808080}\)
Rút gọn
1.left(frac{2}{45}-frac{4}{13}-frac{1}{3}right):left(frac{3}{13}-frac{4}{15}+frac{2}{13}right)
2.frac{0,8:left(frac{4}{5}.1,25right)}{0,64-frac{1}{25}}+frac{left(1,08-frac{2}{15}right):frac{4}{7}}{left(6frac{5}{9}-3frac{1}{4}right)2frac{2}{17}}
3.frac{0,4-frac{2}{9}+frac{2}{11}}{1,4-frac{7}{9}+frac{7}{11}}-frac{frac{1}{3}-0,25+frac{1}{5}}{1frac{1}{6}-0,875+0,7}
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Rút gọn
1.\(\left(\frac{2}{45}-\frac{4}{13}-\frac{1}{3}\right):\left(\frac{3}{13}-\frac{4}{15}+\frac{2}{13}\right)\)
2.\(\frac{0,8:\left(\frac{4}{5}.1,25\right)}{0,64-\frac{1}{25}}+\frac{\left(1,08-\frac{2}{15}\right):\frac{4}{7}}{\left(6\frac{5}{9}-3\frac{1}{4}\right)2\frac{2}{17}}\)
3.\(\frac{0,4-\frac{2}{9}+\frac{2}{11}}{1,4-\frac{7}{9}+\frac{7}{11}}-\frac{\frac{1}{3}-0,25+\frac{1}{5}}{1\frac{1}{6}-0,875+0,7}\)
Thực hiên phép tính:
\(\frac{1}{5}.\frac{4\left(3+\frac{1}{3}-\frac{3}{7}-\frac{3}{53}\right)}{3+\frac{1}{3}-\frac{3}{37}-\frac{3}{53}}:\frac{4+\frac{4}{17}+\frac{4}{19}+\frac{4}{2003}}{5+\frac{5}{17}+\frac{5}{19}+\frac{5}{2003}}\)
Chứng minh :
a) frac{1}{3}-frac{2}{3^2}+frac{3}{3^3}-frac{4}{3^4}+...+frac{99}{3^{99}}-frac{100}{3^{100}} frac{3}{16} frac{1}{3}-frac{2}{3^2}+frac{3}{3^3}+frac{4}{4^4}+...+frac{99}{3^{99}}-frac{100}{3^{100}} frac{3}{16}
b)frac{1}{41}+frac{1}{42}+frac{1}{43}+...+frac{1}{79}+frac{1}{80} frac{7}{12}
c) Cho Sfrac{3}{10}+frac{3}{11}+frac{3}{12}+frac{3}{13}+frac{3}{14}
Chứng minh 1 S 2
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Chứng minh :
a) \(\frac{1}{3}-\frac{2}{3^2}+\frac{3}{3^3}-\frac{4}{3^4}+...+\frac{99}{3^{99}}-\frac{100}{3^{100}}< \frac{3}{16}\) \(\frac{1}{3}-\frac{2}{3^2}+\frac{3}{3^3}+\frac{4}{4^4}+...+\frac{99}{3^{99}}-\frac{100}{3^{100}}< \frac{3}{16}\)
b)\(\frac{1}{41}+\frac{1}{42}+\frac{1}{43}+...+\frac{1}{79}+\frac{1}{80}< \frac{7}{12}\)
c) Cho \(S=\frac{3}{10}+\frac{3}{11}+\frac{3}{12}+\frac{3}{13}+\frac{3}{14}\)
Chứng minh \(1< S< 2\)
Rút gọn
1.\(\frac{7}{19}.\frac{8}{11}+\frac{7}{19}.\frac{3}{11}+\frac{12}{19}\)
2.\(\frac{\frac{2}{5}+\frac{2}{7}-\frac{2}{9}-\frac{2}{11}}{\frac{4}{5}+\frac{4}{7}-\frac{4}{9}-\frac{4}{11}}\)
tính nhanh :a) frac{-3}{7}+frac{15}{26}-left(frac{2}{13}-frac{3}{7}right)b) 2.frac{3}{7}+left(frac{2}{9}-1frac{3}{7}right)-frac{5}{3}:frac{1}{9}c) frac{-11}{23}.frac{6}{7}+frac{8}{7}.frac{-11}{23}-frac{1}{23}d) left(frac{377}{-231}-frac{123}{89}+frac{34}{791}right).left(frac{1}{6}-frac{1}{8}-frac{1}{24}right)
Đọc tiếp
tính nhanh :
a) \(\frac{-3}{7}+\frac{15}{26}-\left(\frac{2}{13}-\frac{3}{7}\right)\)
b) \(2.\frac{3}{7}+\left(\frac{2}{9}-1\frac{3}{7}\right)-\frac{5}{3}:\frac{1}{9}\)
c) \(\frac{-11}{23}.\frac{6}{7}+\frac{8}{7}.\frac{-11}{23}-\frac{1}{23}\)
d) \(\left(\frac{377}{-231}-\frac{123}{89}+\frac{34}{791}\right).\left(\frac{1}{6}-\frac{1}{8}-\frac{1}{24}\right)\)
Mấy bạn giúp mình vớiBài 1:Chứng minh rằng:a)frac{1}{1}-frac{1}{2}+frac{1}{3}-frac{1}{4}+...+frac{1}{9}-frac{1}{10}frac{1}{6}+frac{1}{7}+frac{1}{8}+frac{1}{9}+frac{1}{10}b)frac{1}{1times2}+frac{1}{3times4}+frac{1}{5times6}+...+frac{1}{400}frac{1}{201}+frac{1}{202}+...+frac{1}{400}
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Mấy bạn giúp mình với
Bài 1:Chứng minh rằng:
a)\(\frac{1}{1}-\frac{1}{2}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{9}-\frac{1}{10}=\frac{1}{6}+\frac{1}{7}+\frac{1}{8}+\frac{1}{9}+\frac{1}{10}\)
b)\(\frac{1}{1\times2}+\frac{1}{3\times4}+\frac{1}{5\times6}+...+\frac{1}{400}=\frac{1}{201}+\frac{1}{202}+...+\frac{1}{400}\)
Chứng tỏ:\(\frac{1}{26}+\frac{1}{27}+\frac{1}{28}+...+\frac{1}{49}+\frac{1}{50}=\frac{99}{50}-\frac{97}{45}+...+\frac{7}{4}-\frac{5}{3}=1\)
tính hợp lí nếu có thể
\(-\frac{1}{4}\times13\frac{9}{11}-0,25\times6\frac{2}{11}\)
\(B=\frac{-5}{6}\times\frac{4}{19}+\frac{-7}{12}\times\frac{4}{19}-\frac{40}{57}\)
\(\frac{3}{7}\times\frac{9}{26}-\frac{1}{14}\times\frac{1}{13}-\frac{1}{7}\)
\(\frac{4}{9}:\left(-\frac{1}{7}\right)+6\frac{5}{9}:\left(-\frac{1}{7}\right)\)