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a) 127 + (-18) + (-107) + (-92)
=(-18 + -92) + 127 +(-107)
=(-37) + 127 + (-107)
=90 + (-107)
= -17
b) x- 3) -7= -4
x- 3 = (-4) + 7
x- 3 = 3
x = 3 + 3
x = 6
Vậy x = 6
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\(42+\frac{93}{6}+\frac{87}{12}+\frac{79}{20}+\frac{69}{30}+\frac{57}{42}\)
\(=37+\left(1+\frac{93}{6}\right)+\left(1+\frac{87}{12}\right)+\left(\frac{79}{20}+1\right)+\left(1+\frac{69}{30}\right)+\left(1+\frac{57}{42}\right)\)
\(=37+\frac{99}{6}+\frac{99}{12}+\frac{99}{20}+\frac{99}{30}+\frac{99}{42}\)
\(=37+99\left(\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}\right)\)
\(=37+99\left(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}\right)\)
\(=37+99\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}\right)\)
\(=37+99\left(\frac{1}{2}-\frac{1}{7}\right)\)
\(=37+99.\frac{5}{14}\)
\(=37+35\frac{5}{14}\)
\(=72\frac{5}{14}\)
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\(\dfrac{92}{6}\times\dfrac{72}{15}:\left(-\dfrac{72}{10}\right)\)
\(=\dfrac{92\times72}{6\times15}:\left(-\dfrac{72}{10}\right)\)
\(=\dfrac{368}{5}:\left(-\dfrac{72}{10}\right)\)
\(=\dfrac{368}{5}\times\dfrac{-10}{72}\)
\(=\dfrac{368\times\left(-10\right)}{5\times72}\)
\(=\dfrac{-92}{9}\)
\(=\dfrac{92}{6}\cdot\dfrac{72}{15}\cdot\dfrac{-10}{72}=\dfrac{92}{6}\cdot\dfrac{-2}{3}=\dfrac{-92}{9}\)
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thật sự là sự thật ; sự thật là nhiều quá, mk làm phụ bạn 1 số câu thôi nhá
a) 79-[32*2-9+3(7*23-34)]+14=79-[9*2-9+3(7*8-34)]+14=79-[18-9+3*22]+14=79-75+14=18
b)347{[(63+184)/23]*92}=347{[(216+184)/8]*92}=347[(400/8)*92]=347(50*92)=347*4600=1 596 200
c)85*67-6438/87+31*22=5695-74+124=5745
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-2+6-12+16-22+26-....-92+96
= 4 + 4 +....+ 4
= 4 .10
= 40
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2³.3⁴ + 92.81 - 6³.5
= 8.81 + 92.81 - 216.5
= 81.(8 + 92) - 1080
= 81.100 - 1080
= 8100 - 1080
= 7020
23 . 34+92.81-63.5
=8.81+92.81-216.5
= 81.(8+92)-1080
=81.100-1080
=8100-1080
= 7020
dua thoi gap gap lam mình can so sánh kẹt qua
\(\frac{6}{7.12}+\frac{6}{12.17}+...+\frac{6}{87.92}+\frac{6}{92.95}\)
= \(6\left(\frac{5}{7.12}.\frac{1}{5}+\frac{5}{12.17}.\frac{1}{5}+...+\frac{5}{92.95}.\frac{1}{5}\right)\)
= \(6.\frac{1}{5}\left(\frac{5}{7.12}+\frac{5}{12.17}+...+\frac{5}{87.92}+\frac{5}{92.95}\right)\)
= \(\frac{6}{5}\left(\frac{5}{7}-\frac{5}{12}+\frac{5}{12}-\frac{5}{17}+...+\frac{5}{92}-\frac{5}{95}\right)\)
= \(\frac{6}{5}\left(\frac{5}{7}-\frac{5}{95}\right)\)= \(\frac{6}{5}.\frac{88}{133}=\frac{528}{665}\)
Tự rút gọn, mình lười.