tính nhanh: m= \(\dfrac{1}{3,5}\)+\(\dfrac{1}{5,7}\)+\(\dfrac{1}{7,9}\)+\(\dfrac{1}{9,11}\)+...+\(\dfrac{1}{97,99}\)
Những câu hỏi liên quan
\(\dfrac{1}{3}\)+\(\dfrac{1}{15}\)+\(\dfrac{1}{35}\)+...+\(\dfrac{1}{97,99}\)
Tính tổng trên:
Sửa đề bài xíu nhé !
\(\dfrac{1}{3}+\dfrac{1}{15}+\dfrac{1}{35}+...+\dfrac{1}{97.99}\)
\(=\dfrac{1}{2}.\left(\dfrac{2}{1.3}+\dfrac{2}{3.5}+\dfrac{2}{5.7}+....+\dfrac{2}{97.99}\right)\)
\(=\dfrac{1}{2}.\left(1-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+...+\dfrac{1}{97}-\dfrac{1}{99}\right)\)
\(=\dfrac{1}{2}.\dfrac{98}{99}=\dfrac{49}{99}\)
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1) (-6,5).5,7+5,7.(-3,5)
2) \(\left(1-\dfrac{2}{5}\right)^2\) + \(\dfrac{3}{5}\) + \(\dfrac{-7}{10}\)
chỗ \(\dfrac{3}{5}\) là \(\left|\dfrac{-3}{5}\right|\)
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1: \(=5.7\left(-6.5-3.5\right)=-10\cdot5.7=-57\)
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Tính :
\(M=\left(2\dfrac{1}{3}+3,5\right):\left(-4\dfrac{1}{6}+3\dfrac{1}{7}\right)+7,5\)
\(M=\left(2\dfrac{1}{3}+3,5\right):\left(-4\dfrac{1}{6}+3\dfrac{1}{7}\right)+7,5\)
\(M=\left(\dfrac{7}{3}+\dfrac{7}{2}\right):\left(-\dfrac{25}{6}+\dfrac{22}{7}\right)+\dfrac{15}{2}\)
\(M=\dfrac{35}{6}:\left(-\dfrac{43}{42}\right)+\dfrac{15}{2}\)
\(M=\left(-\dfrac{245}{43}\right)+\dfrac{15}{2}\)
\(M=\dfrac{155}{86}\)
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M=(213+3,5):(−416+317)+7,5M=(213+3,5):(−416+317)+7,5
M=(73+72):(−256+227)+152M=(73+72):(−256+227)+152
M=356:(−4342)+152M=356:(−4342)+152
M=(−24543)+152M=(−24543)+152
M=15586M=15586
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Tính nhanh
\(\dfrac{1}{20}\)+\(\dfrac{1}{30}\)+\(\dfrac{1}{42}\)+\(\dfrac{1}{56}\)+\(\dfrac{1}{72}\)+\(\dfrac{1}{90}\)+\(\dfrac{1}{110}\)+\(\dfrac{1}{132}\)
=
A = \(\dfrac{1}{20}\) + \(\dfrac{1}{30}\) + \(\dfrac{1}{42}\) + \(\dfrac{1}{56}\) + \(\dfrac{1}{72}\) + \(\dfrac{1}{90}\) + \(\dfrac{1}{110}\) + \(\dfrac{1}{132}\)
A = \(\dfrac{1}{4\times5}\) + \(\dfrac{1}{5\times6}\) + \(\dfrac{1}{6\times7}\)+ \(\dfrac{1}{7\times8}\)+\(\dfrac{1}{8\times9}\)+ \(\dfrac{1}{9\times10}\) + \(\dfrac{1}{10\times11}\)+\(\dfrac{1}{11\times12}\)
A = \(\dfrac{1}{4}\)-\(\dfrac{1}{5}\) +\(\dfrac{1}{5}\)-\(\dfrac{1}{6}\) +.....+\(\dfrac{1}{11}\) - \(\dfrac{1}{12}\)
A = \(\dfrac{1}{4}\) - \(\dfrac{1}{12}\)
A = \(\dfrac{1}{6}\)
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\(\dfrac{1}{2}\)+\(\dfrac{1}{4}\)+\(\dfrac{1}{8}\)+\(\dfrac{1}{16}\)+\(\dfrac{1}{32}\)+\(\dfrac{1}{64}\)+\(\dfrac{1}{128}\)+\(\dfrac{1}{256}\)
Tính nhanh
23 tháng 5 2022 lúc 19:30
Tính nhanh:\((\) \(\dfrac{1}{3}\)-\(\dfrac{1}{5}\)-\(\dfrac{1}{10}\)-\(\dfrac{1}{30}\))x(\(\dfrac{1}{21}\)+\(\dfrac{1}{210}\)+\(\dfrac{1}{2010}\))
\(=\left(\dfrac{1}{21}+\dfrac{1}{210}+\dfrac{1}{2010}\right)\cdot\dfrac{10-6-3-1}{30}=0\)
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\(\left(\dfrac{1}{3}-\dfrac{1}{5}-\dfrac{1}{10}-\dfrac{1}{30}\right)\times\left(\dfrac{1}{21}+\dfrac{1}{210}+\dfrac{1}{2010}\right)\)
\(=\left(\dfrac{10}{30}-\dfrac{6}{30}-\dfrac{3}{30}-\dfrac{1}{30}\right)\times\left(\dfrac{1}{21}+\dfrac{1}{210}+\dfrac{1}{2010}\right)\)
\(=0\times\left(\dfrac{1}{21}+\dfrac{1}{210}+\dfrac{1}{2010}\right)\)
\(=0\)
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Bài 1:Tính bằng cách hợp lý (nếu có thể)
a,16dfrac{2}{7}:left(dfrac{-3}{5}right)+28dfrac{2}{7}:dfrac{3}{5}
b,dfrac{3}{5}:left(dfrac{-1}{15}-dfrac{1}{6}right)+dfrac{3}{5}:left(dfrac{-1}{3}-1dfrac{1}{15}right)
c,left(-6,5right).5,7+5,7.left(-3.5right)
d,10.sqrt{0,01.}sqrt{ }dfrac{16}{9}+3sqrt{49}-dfrac{1}{6}sqrt{4}
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Bài 1:Tính bằng cách hợp lý (nếu có thể)
a,\(16\dfrac{2}{7}:\left(\dfrac{-3}{5}\right)+28\dfrac{2}{7}:\dfrac{3}{5}\)
b,\(\dfrac{3}{5}:\left(\dfrac{-1}{15}-\dfrac{1}{6}\right)+\dfrac{3}{5}:\left(\dfrac{-1}{3}-1\dfrac{1}{15}\right)\)
c,\(\left(-6,5\right).5,7+5,7.\left(-3.5\right)\)
d,\(10.\sqrt{0,01.}\sqrt{ }\dfrac{16}{9}+3\sqrt{49}-\dfrac{1}{6}\sqrt{4}\)
a: \(=\dfrac{5}{3}\cdot\left(-16-\dfrac{2}{7}\right)+\dfrac{5}{3}\cdot\left(28+\dfrac{2}{7}\right)\)
\(=\dfrac{5}{3}\left(-16-\dfrac{2}{7}+28+\dfrac{2}{7}\right)\)
\(=\dfrac{5}{3}\cdot12=20\)
b: \(=\dfrac{3}{5}:\left(\dfrac{-2-5}{30}\right)+\dfrac{3}{5}:\left(\dfrac{-1}{3}-\dfrac{16}{15}\right)\)
\(=\dfrac{3}{5}:\dfrac{-7}{30}+\dfrac{3}{5}:\dfrac{-21}{15}\)
\(=\dfrac{3}{5}\left(\dfrac{-30}{7}-\dfrac{15}{21}\right)=\dfrac{3}{5}\cdot\left(\dfrac{-30}{7}-\dfrac{5}{7}\right)=\dfrac{3}{5}\cdot\left(-5\right)=-3\)
c: \(=5.7\left(-6.5-3.5\right)\)
\(=5.7\cdot\left(-10\right)=-57\)
d: \(=10\cdot0.1\cdot\dfrac{4}{3}+3\cdot7-\dfrac{1}{6}\cdot2\)
\(=\dfrac{4}{3}+21-\dfrac{1}{3}=22\)
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Tính nhanh
a, S dfrac{1}{3} + dfrac{1}{15} + dfrac{1}{35} + dfrac{1}{63} + dfrac{1}{99} + dfrac{1}{143}
b, A dfrac{1}{3} + dfrac{1}{6} + dfrac{1}{10} + dfrac{1}{15} + dfrac{1}{21} + dfrac{1}{28}
c, H dfrac{4047991-2010x2009}{4050000-2011x2009}
d, T dfrac{2009x20010+2000}{2011x2010-2020}
e, P dfrac{7589-80,5x69,3}{7485,05-79x69,3}
f, B 5,1 x 42,2 + 1,7 x 448 x 3 - 0,15 x 700
Giúp mình với
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Tính nhanh
a, S= \(\dfrac{1}{3}\) + \(\dfrac{1}{15}\) + \(\dfrac{1}{35}\) + \(\dfrac{1}{63}\) + \(\dfrac{1}{99}\) + \(\dfrac{1}{143}\)
b, A = \(\dfrac{1}{3}\) + \(\dfrac{1}{6}\) + \(\dfrac{1}{10}\) + \(\dfrac{1}{15}\) + \(\dfrac{1}{21}\) + \(\dfrac{1}{28}\)
c, H =\(\dfrac{4047991-2010x2009}{4050000-2011x2009}\)
d, T = \(\dfrac{2009x20010+2000}{2011x2010-2020}\)
e, P = \(\dfrac{7589-80,5x69,3}{7485,05-79x69,3}\)
f, B = 5,1 x 42,2 + 1,7 x 448 x 3 - 0,15 x 700
Giúp mình với
a=78/35
b=22/12
c=1/1
d=40202090/4040090
e=1,24025667172...
f=871,82
ko biết đúng ko [0_0'] hihi
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tính nhanh \(\dfrac{1}{2}\) +\(\dfrac{1}{4}\) +\(\dfrac{1}{8}\)+\(\dfrac{1}{16}\) +.....+\(\dfrac{1}{512}\) +\(\dfrac{1}{1024}\)
Đặt A=1/2+1/4+1/8+..+1/1024
Ax2=1+1/2+1/4+1/8+..+1/512( Nhân cả 2 vế với 2)
Ax2-A=(1+1/2+1/4+1/8+..+1/512)-(1/2+1/4+1/8+..+1/1024)
<=>A=1-1/1024
<=>A=1023/1024
Vậy biểu thức đã cho = 1023/1024
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