1.Tính nhanh:
e)\(\dfrac{\dfrac{1}{6}-\dfrac{1}{39}+\dfrac{1}{51}}{\dfrac{1}{8}-\dfrac{1}{12}+\dfrac{1}{68}}\)
f)\(\dfrac{7}{8}+\dfrac{7}{56}+\dfrac{7}{154}+...+\dfrac{7}{1400}\)
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Bài 1: Tính nhanh
\(A=\dfrac{1}{4}.\dfrac{7}{3}.12\)
\(B=\dfrac{3}{8}.56.\dfrac{25}{7}.\left(-4\right)\)
\(C=\dfrac{6}{7}.\dfrac{8}{13}+\dfrac{6}{13}.\dfrac{9}{7}-\dfrac{3}{13}.\dfrac{6}{7}\)
\(D=\dfrac{-1}{4}.\dfrac{152}{11}+\dfrac{68}{4}.\dfrac{-1}{11}\)
A = \(\dfrac{1}{4}.\dfrac{7}{3}.12\)
= \(\dfrac{1.7.12}{4.3}\)
= \(7\)
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B = \(\dfrac{3}{8}.56.\dfrac{25}{7}.\left(-4\right)\)
= \(-\dfrac{3.56.25.4}{8.7}\)
= -3.100
= -300
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C = \(\dfrac{6}{7}.\dfrac{8}{13}+\dfrac{6}{13}.\dfrac{9}{7}-\dfrac{3}{13}.\dfrac{6}{7}\)
= \(\dfrac{8}{7}.\dfrac{6}{13}+\dfrac{6}{13}.\dfrac{9}{7}-\dfrac{6}{13}.\dfrac{3}{7}\)
= \(\dfrac{6}{13}\left(\dfrac{8}{7}+\dfrac{9}{7}-\dfrac{3}{7}\right)\)
= \(\dfrac{6}{13}\left(\dfrac{8+9-3}{7}\right)\)
= \(\dfrac{6}{13}.2\)
= \(\dfrac{12}{13}\)
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25 tháng 1 2022 lúc 21:25
e) D = \(\dfrac{-5}{6}+\dfrac{-7}{12}-\dfrac{1}{3}\)
f) F = \(\dfrac{-3}{4}+\dfrac{1}{3}-\dfrac{-5}{18}\)
g) G = \(\dfrac{19}{9}-\dfrac{-4}{11}+\dfrac{2}{3}\)
h) H = \(\dfrac{5}{12}+\dfrac{-7}{4}-\dfrac{1}{-8}\)
e: \(D=\dfrac{-10}{12}-\dfrac{7}{12}-\dfrac{4}{12}=\dfrac{-21}{12}=-\dfrac{7}{4}\)
f: \(F=\dfrac{-27}{36}+\dfrac{12}{36}+\dfrac{10}{36}=\dfrac{-5}{36}\)
g: \(G=\dfrac{209}{99}+\dfrac{36}{99}+\dfrac{66}{99}=\dfrac{311}{99}\)
h: \(H=\dfrac{10}{24}-\dfrac{42}{24}+\dfrac{3}{24}=-\dfrac{29}{24}\)
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\(D=\dfrac{-5}{6}+\dfrac{-7}{12}-\dfrac{1}{3}=-\dfrac{7}{4}\)
\(F=\dfrac{-3}{4}+\dfrac{1}{3}-\dfrac{-5}{18}=-\dfrac{5}{36}\)
\(G=\dfrac{19}{9}-\dfrac{-4}{11}+\dfrac{2}{3}=\dfrac{311}{99}\)
\(H=\dfrac{5}{12}+\dfrac{-7}{4}-\dfrac{1}{-8}=-\dfrac{29}{24}\)
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\(e,D=\dfrac{-5}{6}+\dfrac{-7}{12}-\dfrac{1}{3}=\dfrac{-10}{12}+\dfrac{-7}{12}-\dfrac{4}{12}=\dfrac{\left(-10\right)+\left(-7\right)-4}{12}=\dfrac{-21}{12}=\dfrac{-7}{4}\\ f,F=\dfrac{-3}{4}+\dfrac{1}{3}-\dfrac{-5}{18} =\dfrac{-27}{36}+\dfrac{12}{36}-\dfrac{-10}{36}=\dfrac{\left(-27\right)+12-\left(-10\right)}{36}=\dfrac{-5}{36}\)
\(g,G=\dfrac{19}{9}-\dfrac{-4}{11}+\dfrac{2}{3}=\dfrac{209}{99}-\dfrac{-36}{99}+\dfrac{66}{99}=\dfrac{209-\left(-36\right)+66}{99}=\dfrac{311}{99}\\ h,H=\dfrac{5}{12}+\dfrac{-7}{4}-\dfrac{1}{-8}=\dfrac{5}{12}-\dfrac{7}{4}+\dfrac{1}{8}=\dfrac{10}{24}-\dfrac{42}{24}+\dfrac{3}{24}=\dfrac{10-42+3}{24}=\dfrac{-29}{24}\)
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Tính nhanh
a)(5dfrac{1}{7}- 3dfrac{3}{11}) - 2dfrac{1}{7}-1dfrac{8}{11}
b) (dfrac{1999}{2011}-dfrac{2011}{1999}) -(dfrac{-12}{1999}-dfrac{12}{2011})
c)(1-dfrac{1}{2})(1-dfrac{1}{3})............(1-dfrac{1}{2017})
d) dfrac{2}{15}.6dfrac{5}{11}+dfrac{5}{11}.dfrac{-2}{15}-dfrac{2}{15}.2015^0
e)dfrac{1}{6}-dfrac{1}{39}+dfrac{1}{51}:dfrac{1}{8}-dfrac{1}{12}+dfrac{1}{68}
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Tính nhanh
a)(5\(\dfrac{1}{7}\)- 3\(\dfrac{3}{11}\)) - 2\(\dfrac{1}{7}\)-1\(\dfrac{8}{11}\)
b) (\(\dfrac{1999}{2011}-\dfrac{2011}{1999}\)) -(\(\dfrac{-12}{1999}-\dfrac{12}{2011}\))
c)(1-\(\dfrac{1}{2}\))(1-\(\dfrac{1}{3}\))............(1-\(\dfrac{1}{2017}\))
d) \(\dfrac{2}{15}.6\dfrac{5}{11}+\dfrac{5}{11}.\dfrac{-2}{15}\)\(-\dfrac{2}{15}.2015^0\)
e)\(\dfrac{1}{6}-\dfrac{1}{39}+\dfrac{1}{51}\):\(\dfrac{1}{8}-\dfrac{1}{12}+\dfrac{1}{68}\)
Đây này má Ran mori
a) \(\left(5\dfrac{1}{7}-3\dfrac{3}{11}\right)-2\dfrac{1}{7}-1\dfrac{8}{11}\)
\(=5+\dfrac{1}{7}-3-\dfrac{3}{11}-2-\dfrac{1}{7}-1-\dfrac{8}{11}\)
\(=\left(5-3-2-1\right)+\left(\dfrac{1}{7}-\dfrac{3}{11}-\dfrac{1}{7}-\dfrac{8}{11}\right)\)
\(=-1+\left(\dfrac{1}{7}-\dfrac{1}{7}\right)-\left(\dfrac{3}{11}+\dfrac{8}{11}\right)\)
\(=-1+0-1=-2\)
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a)\(\left(5\dfrac{1}{7}-3\dfrac{3}{11}\right)-2\dfrac{1}{7}-1\dfrac{8}{11}\)
= \(\left(5+\dfrac{1}{7}-3+\dfrac{3}{11}\right)-2+\dfrac{1}{7}-1+\dfrac{8}{11}\)
= \(5-\dfrac{1}{7}+3-\dfrac{3}{11}-2+\dfrac{1}{7}-1+\dfrac{8}{11}\)
= \(\left(5-3-2-1\right)+\dfrac{1}{7}+\dfrac{1}{7}+\dfrac{8}{11}-\dfrac{3}{11}\)
= \(-1+2+\dfrac{5}{11}\)
= \(1+\dfrac{5}{11}=\dfrac{1}{1}+\dfrac{5}{11}=\dfrac{11}{11}+\dfrac{5}{11}=\dfrac{16}{11}\)
Vậy :câu a) = \(\dfrac{16}{11}\)
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Tính nhanh:
a, \(\dfrac{8}{9}-\dfrac{1}{72}-\dfrac{1}{56}-\dfrac{1}{42}-\dfrac{1}{30}-\dfrac{1}{20}-\dfrac{1}{12}-\dfrac{1}{6}-\dfrac{1}{2}\)
b, \(\left(-\dfrac{1}{4}+\dfrac{7}{35}-\dfrac{5}{3}\right)-\left(-\dfrac{15}{12}+\dfrac{6}{11}-\dfrac{48}{49}\right)\)
a: Ta có: \(\dfrac{8}{9}-\left(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+...+\dfrac{1}{72}\right)\)
\(=\dfrac{8}{9}-\left(1-\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{3}-...+\dfrac{1}{8}-\dfrac{1}{9}\right)\)
=0
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Tìm x, biết :
a) left(dfrac{31}{20}-dfrac{26}{45}right).dfrac{-36}{35} x left(dfrac{51}{56}+dfrac{8}{21}+dfrac{1}{3}right).dfrac{8}{13}
b) dfrac{-3}{5}.xdfrac{1}{4}+0,75
c) left(dfrac{1}{7}-dfrac{1}{3}right).xdfrac{28}{3}.left(dfrac{1}{4}-dfrac{1}{7}right)
d) dfrac{5}{7}.xdfrac{9}{8}-0,125
e)left(dfrac{2}{11}+dfrac{1}{3}right).xleft(dfrac{1}{7}-dfrac{1}{8}right).56
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Tìm x, biết :
a) \(\left(\dfrac{31}{20}-\dfrac{26}{45}\right).\dfrac{-36}{35}< x< \left(\dfrac{51}{56}+\dfrac{8}{21}+\dfrac{1}{3}\right).\dfrac{8}{13}\)
b) \(\dfrac{-3}{5}.x=\dfrac{1}{4}+0,75\)
c) \(\left(\dfrac{1}{7}-\dfrac{1}{3}\right).x=\dfrac{28}{3}.\left(\dfrac{1}{4}-\dfrac{1}{7}\right)\)
d) \(\dfrac{5}{7}.x=\dfrac{9}{8}-0,125\)
e)\(\left(\dfrac{2}{11}+\dfrac{1}{3}\right).x=\left(\dfrac{1}{7}-\dfrac{1}{8}\right).56\)
Mấy bài này bạn tự làm đi, chuyển vế tìm x gần giống cấp I mà.
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b)\(\dfrac{-3}{5}.x=\dfrac{1}{4}+0,75\)
=>\(\dfrac{-3}{5}.x=1\)
=>\(x=1:\dfrac{-3}{5}\)
=>\(x=\dfrac{-5}{3}\)
Vậy \(x=\dfrac{-5}{3}\)
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BT2: Tính nhanh
1) \(\dfrac{5}{6}-\dfrac{6}{7}+\dfrac{7}{8}-\dfrac{8}{9}+\dfrac{10}{9}-\dfrac{5}{6}+\dfrac{6}{7}-\dfrac{7}{8}+\dfrac{8}{9}\)
2) \(\dfrac{1}{13}+\dfrac{16}{7}+\dfrac{3}{105}-\dfrac{9}{7}-\dfrac{-12}{13}\)
1) \(\dfrac{5}{6}-\dfrac{6}{7}+\dfrac{7}{8}-\dfrac{8}{9}+\dfrac{10}{9}-\dfrac{5}{6}+\dfrac{6}{7}-\dfrac{7}{8}+\dfrac{8}{9}\)
\(=\left(\dfrac{5}{6}-\dfrac{5}{6}\right)-\left(\dfrac{6}{7}+\dfrac{6}{7}\right)+\left(\dfrac{7}{8}-\dfrac{7}{8}\right)-\left(\dfrac{8}{9}+\dfrac{8}{9}\right)+\dfrac{10}{9}\)
\(=0-0+0-0+\dfrac{10}{9}\)
\(=\dfrac{10}{9}\)
2) \(\dfrac{1}{13}+\dfrac{16}{7}+\dfrac{3}{105}-\dfrac{9}{7}-\dfrac{-12}{13}\)
\(=\left(\dfrac{1}{13}-\left(-\dfrac{12}{13}\right)\right)+\left(\dfrac{16}{7}-\dfrac{9}{7}\right)+\dfrac{3}{105}\)
\(=1+1+\dfrac{3}{105}\)
\(=\dfrac{213}{105}=\dfrac{71}{35}\)
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8 tháng 7 2023 lúc 10:05
tính thuận tiện:dfrac{4}{5}+dfrac{2}{3}+dfrac{1}{5}+dfrac{1}{3} dfrac{17}{12}+dfrac{29}{7}-dfrac{8}{7}+dfrac{7}{12} dfrac{9}{15}+dfrac{16}{7}+dfrac{2}{5}-dfrac{1}{7}-dfrac{2}{14} dfrac{2}{5}+dfrac{6}{9}+dfrac{7}{4}+dfrac{3}{5}+dfrac{1}{3}+dfrac{1}{4}mik sẽ chỉ tick 3 bn xong trước phải chi tiết rõ ràng
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tính thuận tiện:
\(\dfrac{4}{5}+\dfrac{2}{3}+\dfrac{1}{5}+\dfrac{1}{3}\) \(\dfrac{17}{12}+\dfrac{29}{7}-\dfrac{8}{7}+\dfrac{7}{12}\) \(\dfrac{9}{15}+\dfrac{16}{7}+\dfrac{2}{5}-\dfrac{1}{7}-\dfrac{2}{14}\)
\(\dfrac{2}{5}+\dfrac{6}{9}+\dfrac{7}{4}+\dfrac{3}{5}+\dfrac{1}{3}+\dfrac{1}{4}\)
mik sẽ chỉ tick 3 bn xong trước phải chi tiết rõ ràng
a: =4/5+1/5+2/3+1/3=1+1=2
b: =17/12+7/12+29/7-8/7=3+2=5
c: =3/5+2/5+16/7-1/7-1/7
=1+2=3
d: =2/5+3/5+2/3+1/3+7/4+1/4
=1+1+2
=4
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\(\dfrac{4}{5}+\dfrac{2}{3}+\dfrac{1}{5}+\dfrac{1}{3}\)
\(=\left(\dfrac{4}{5}+\dfrac{1}{5}\right)+\left(\dfrac{2}{3}+\dfrac{1}{3}\right)\)
\(=\dfrac{5}{5}+\dfrac{3}{3}\)
\(=1+1\)
\(=2\)
============
\(\dfrac{17}{12}+\dfrac{29}{7}-\dfrac{8}{7}+\dfrac{7}{12}\)
\(=\left(\dfrac{17}{12}+\dfrac{7}{12}\right)+\left(\dfrac{29}{7}-\dfrac{8}{7}\right)\)
\(=\dfrac{24}{12}+\dfrac{21}{7}\)
\(=2+3\)
\(=5\)
====================
\(\dfrac{9}{15}+\dfrac{16}{7}+\dfrac{2}{5}-\dfrac{1}{7}-\dfrac{2}{14}\)
\(=\dfrac{9}{15}+\dfrac{16}{7}+\dfrac{6}{15}-\dfrac{1}{7}-\dfrac{1}{7}\)
\(=\left(\dfrac{9}{15}+\dfrac{6}{15}\right)+\left(\dfrac{16}{7}-\dfrac{1}{7}-\dfrac{1}{7}\right)\)
\(=\dfrac{15}{15}+\dfrac{14}{7}\)
\(=1+2\)
\(=3\)
===============
\(\dfrac{2}{5}+\dfrac{6}{9}+\dfrac{7}{4}+\dfrac{3}{5}+\dfrac{1}{3}+\dfrac{1}{4}\)
\(=\dfrac{2}{5}+\dfrac{2}{3}+\dfrac{7}{4}+\dfrac{3}{5}+\dfrac{1}{3}+\dfrac{1}{4}\)
\(=\left(\dfrac{2}{5}+\dfrac{3}{5}\right)+\left(\dfrac{2}{3}+\dfrac{1}{3}\right)+\left(\dfrac{7}{4}+\dfrac{1}{4}\right)\)
\(=\dfrac{5}{5}+\dfrac{3}{3}+\dfrac{8}{4}\)
\(=1+1+2\)
\(=4\)
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a)dfrac{2}{7}+dfrac{-3}{8}+dfrac{11}{7}+dfrac{1}{7}_{ }+dfrac{5}{-8}
b)dfrac{3}{17}+dfrac{-5}{13}+dfrac{-18}{35}+dfrac{14}{17}+dfrac{17}{-35}_{ }+dfrac{-8}{13}
c)dfrac{-3}{8}+dfrac{12}{25}+dfrac{5}{-8}+dfrac{2}{-5}+dfrac{13}{25}
d)dfrac{-5}{21}+left(dfrac{-16}{21}+1right)
e)dfrac{-3}{17}+left(dfrac{2}{3}+dfrac{3}{17}right)
f)left(dfrac{-1}{6}+dfrac{5}{-12}right)+dfrac{7}{12}
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a)\(\dfrac{2}{7}+\dfrac{-3}{8}+\dfrac{11}{7}+\dfrac{1}{7}_{ }+\dfrac{5}{-8}\)
b)\(\dfrac{3}{17}+\dfrac{-5}{13}+\dfrac{-18}{35}+\dfrac{14}{17}+\dfrac{17}{-35}_{ }+\dfrac{-8}{13}\)
c)\(\dfrac{-3}{8}+\dfrac{12}{25}+\dfrac{5}{-8}+\dfrac{2}{-5}+\dfrac{13}{25}\)
d)\(\dfrac{-5}{21}+\left(\dfrac{-16}{21}+1\right)\)
e)\(\dfrac{-3}{17}+\left(\dfrac{2}{3}+\dfrac{3}{17}\right)\)
f)\(\left(\dfrac{-1}{6}+\dfrac{5}{-12}\right)+\dfrac{7}{12}\)
Các bạn không cần trả lời câu hỏi trên của mik vì mik đã hiểu rồi nha . Cho nên đừng trả lời ! OK
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a,\(\dfrac{2}{9}+\dfrac{1}{6}\)
b,\(\dfrac{5}{6}-\dfrac{4}{7}\)
c,\(\dfrac{3}{8}\)x\(\dfrac{6}{15}\)
d,\(\dfrac{7}{12}:\dfrac{4}{7}\)
e,\(\dfrac{4}{7}:3\)
a,2/9+1/6=7/18
b,5/6-4/7=11/42
c,3/8.6/15=3/20
d,7/12:4/7=49/48
e,4/7:3=4/21
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a: 2/9+1/6=4/18+3/18=7/18
b: 5/6-4/7=35/42-24/42=11/42
c: 3/8x6/15=18/120=3/20
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