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LM
Lê Minh Vũ
VIP
14 tháng 6 2023
\(\left(-\dfrac{1}{2}\right)^2\div\dfrac{1}{4}-2\times\left(-\dfrac{1}{2}\right)^2\\= \dfrac{1}{4}\div\dfrac{1}{4}-2\times\dfrac{1}{4}\\ =1-\dfrac{1}{2}\\ =\dfrac{1}{2}\)
\(\left(-2\right)^3\times-\dfrac{1}{24}+\left(\dfrac{4}{3}-1\dfrac{5}{6}\right)\div\dfrac{5}{12}\)
= \(-6\times-\dfrac{1}{24}+\left(\dfrac{4}{3}-\dfrac{11}{6}\right)\div\dfrac{5}{12}\)
= \(\dfrac{1}{4}+-\dfrac{1}{2}\div\dfrac{5}{12}\)
= \(\dfrac{1}{4}+-\dfrac{6}{5}\)
= \(\dfrac{1}{4}-\dfrac{6}{5}\)
= \(-\dfrac{19}{20}\)
\(\left(6\dfrac{4}{9}+\dfrac{7}{11}\right)-\left(4\dfrac{4}{9}-2\dfrac{4}{11}\right)\\ =\dfrac{58}{9}+\dfrac{7}{11}-\dfrac{40}{9}+\dfrac{26}{11}\\ =\dfrac{58}{9}-\dfrac{40}{9}+\dfrac{7}{11}+\dfrac{26}{11}\\ =12+3\\ =15\)
TA
14 tháng 6 2023
\(a,\left(\dfrac{-1}{2}\right)^2:\dfrac{1}{4}-2\left(-\dfrac{1}{2}\right)^2\)
\(=\left(-\dfrac{1}{2}\right)^2\left(4-2\right)\)
\(=\dfrac{1}{4}.2=\dfrac{1}{2}\)
\(b,\left(-2\right)^3.\dfrac{-1}{24}+\left(\dfrac{4}{3}-1\dfrac{5}{6}\right):\dfrac{5}{12}\)
\(=\left(-8\right).\dfrac{-1}{24}+\left(-\dfrac{1}{2}\right).\dfrac{12}{5}\)
\(=\dfrac{1}{3}+\left(-\dfrac{1}{5}\right)=\dfrac{2}{15}\)
\(c,\left(6\dfrac{4}{9}+\dfrac{7}{11}\right)-\left(4\dfrac{4}{9}-2\dfrac{4}{11}\right)\)
\(=\dfrac{701}{99}-\dfrac{206}{99}=\dfrac{495}{99}=5\)
\(d,10\dfrac{1}{5}-5\dfrac{1}{2}.\dfrac{60}{11}+\dfrac{3}{15\%}\)
\(=\dfrac{51}{5}-30+20=\dfrac{1}{5}\)
\(e,\dfrac{5}{7}.\dfrac{5}{11}+\dfrac{5}{7}.\dfrac{2}{11}-\dfrac{5}{7}.\dfrac{14}{11}\)
\(=\dfrac{5}{7}\left(\dfrac{5}{11}+\dfrac{2}{11}-\dfrac{14}{11}\right)=\dfrac{5}{7}.\left(-\dfrac{7}{11}\right)\)
\(=-\dfrac{5}{11}\)
\(f,\dfrac{-5}{7}.\dfrac{2}{11}+\left(-\dfrac{5}{7}\right).\dfrac{9}{11}+1\dfrac{5}{7}\)
\(=\left(-\dfrac{5}{7}\right)\left(\dfrac{2}{11}+\dfrac{9}{11}\right)+\dfrac{12}{7}\)
\(=\left(-\dfrac{5}{7}\right)+\dfrac{12}{7}=1\)
AT
21 tháng 3 2017
Dễ thế cũng hỏi ở trường tính hay lắm mà:
a) \(\dfrac{3}{7}.\dfrac{8}{11}+\dfrac{3}{7}.\dfrac{5}{11}-\dfrac{3}{7}.\dfrac{2}{11}\)
\(=\dfrac{3}{7}.\left(\dfrac{8}{11}+\dfrac{5}{11}-\dfrac{2}{11}\right)\)
\(=\dfrac{3}{7}.\left(\dfrac{8+5-2}{11}\right)=\dfrac{3}{7}.\dfrac{11}{11}=\dfrac{3}{7}\)
b) \(\dfrac{3}{13}.\dfrac{8}{25}+\dfrac{3}{13}.\dfrac{11}{25}+\dfrac{3}{13}.\dfrac{6}{25}-\dfrac{3}{13}\)
\(=\dfrac{3}{13}.\left(\dfrac{8}{25}+\dfrac{11}{25}+\dfrac{6}{25}-1\right)\)
\(=\dfrac{3}{13}.\left(\dfrac{8+11+6}{25}-1=\right)\dfrac{3}{13}.0=0\)
21 tháng 3 2017
a,
\(\dfrac{3}{7}.\dfrac{8}{11}+\dfrac{3}{7}.\dfrac{5}{11}-\dfrac{3}{7}.\dfrac{2}{11}=\dfrac{3}{7}\left(\dfrac{8}{11}+\dfrac{5}{11}-\dfrac{2}{11}\right)=\dfrac{3}{7}.1=\dfrac{3}{7}\)
b,
\(\dfrac{3}{13}.\dfrac{8}{25}+\dfrac{3}{13}.\dfrac{11}{25}+\dfrac{3}{13}.\dfrac{6}{25}-\dfrac{3}{13}=\dfrac{3}{13}\left(\dfrac{8}{25}+\dfrac{11}{25}+\dfrac{6}{25}-1\right)=\dfrac{3}{13}.0=0\)
2 tháng 5 2019
a) \(\frac{8}{40}+\frac{-14}{35}-\frac{12}{60}\)
= \(\frac{1}{5}-\frac{2}{5}-\frac{1}{5}\)
= \(\left(\frac{1}{5}-\frac{1}{5}\right)-\frac{2}{5}\)
= \(-\frac{2}{5}\)
b) 5/7.5/11 + 5/7.5/11 - 5/7.14/11
= 5/7.(5/11 + 5/11 - 14/11)
= 5/7.(-4/11)
= -20/77
c) \(19\frac{5}{8}:\frac{7}{12}-15\frac{1}{4}:\frac{7}{12}\)
= \(\left(19\frac{5}{8}-15\frac{1}{4}\right):\frac{7}{12}\)
= \(\frac{35}{8}:\frac{7}{12}\)
= \(\frac{15}{2}\)
2 tháng 5 2019
d) 2/5.1/3 - 2/15 : 1/5 + 3/5.1/3
= (2/5 + 3/5).1/3 - 2/15 . 5
= 1.1/3 - 2/3
= 1/3 - 2/3
= -1/3
e) \(\frac{4}{9}.19\frac{1}{3}-\frac{4}{9}.39\frac{1}{3}\)
= \(\frac{4}{9}.\left(19\frac{1}{3}-39\frac{1}{3}\right)\)
= \(\frac{4}{9}.\left(-20\right)\)
= \(\frac{-80}{9}\)
g) \(\frac{81.17-15.81}{81.17-81.15}\)
= 1
NT
2
14 tháng 7 2021
a) Ta có: \(\dfrac{3}{5\cdot7}+\dfrac{3}{7\cdot9}+...+\dfrac{3}{59\cdot61}\)
\(=\dfrac{3}{2}\left(\dfrac{2}{5\cdot7}+\dfrac{2}{7\cdot9}+...+\dfrac{2}{59\cdot61}\right)\)
\(=\dfrac{3}{2}\left(\dfrac{1}{5}-\dfrac{1}{61}\right)\)
\(=\dfrac{3}{2}\cdot\dfrac{56}{305}=\dfrac{84}{305}\)
E
2
HQ
Hà Quang Minh
Giáo viên
2 tháng 8 2023
Em nhớ nhân 1/2 trong tất cả dấu bằng thì biểu thức này mới không thay đổi kết quả nhé.
KS
2 tháng 8 2023
`11/(5.7) + 11/(7.9) + 11/(9.11) + ... + 11/(59.61)`
`= 2.(11/(5.7) + 11/(7.9) + ... + 11/(59.61))`
`= 11.(2/(5.7) + 2/(7.9) + ... + 2/(59.61))`
`= 11.(1/5 - 1/7 + 1/7 - 1/9 + ... +1/59 - 1/61)`
`= 11.(1/5 - 1/61)`
`= 11.56/305`
`= 616/305`
3/7.9/11+3/7.5/11-3/7.25/11
=3/7.(9/11+5/11-25/11)
=3/7.(-1)
=-3/7
`3/7. 9/11+3/7. 5/11-3/7. 25/11`
`= 3/7 . (9/11 +5/11) -3/7 . 25/11`
`= 3/7 . 14/11 - 3/7 . 25/11`
`=3/7 . (14/11-25/11)`
`=3/7 . (-1)`
`=-3/7`