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HQ
Hà Quang Minh
Giáo viên
5 tháng 10 2023

a) \(\dfrac{3}{5} - \dfrac{{ - 1}}{3}\)

\( = \dfrac{{3.3}}{{5.3}} - \dfrac{{ - 1.5}}{{3.5}}\)

\( = \dfrac{9}{{15}} - \dfrac{{ - 5}}{{15}} = \dfrac{{9 - \left( { - 5} \right)}}{{15}} = \dfrac{{14}}{{15}}\)

b) \( - 3 - \dfrac{2}{7}\)

\(\begin{array}{l} = \dfrac{{ - 3.7}}{{1.7}} - \dfrac{2}{7}\\ = \dfrac{{ - 21}}{7} - \dfrac{2}{7}\\ = \dfrac{{ - 21 - 2}}{7}\\ = \dfrac{{ - 23}}{7}\end{array}\)

a: \(=\dfrac{-7}{8}\left(\dfrac{3}{5}+\dfrac{2}{5}\right)+3+\dfrac{7}{8}=\dfrac{-7}{8}+\dfrac{7}{8}+3=3\)

b: \(=-\dfrac{8}{5}:\dfrac{5}{3}=-\dfrac{24}{25}\)

c: \(=\dfrac{6}{7}+\dfrac{1}{8}-\dfrac{3}{4}=\dfrac{6}{7}+\dfrac{1}{8}-\dfrac{6}{8}=\dfrac{6}{7}-\dfrac{5}{8}=\dfrac{48}{56}-\dfrac{35}{56}=\dfrac{13}{56}\)

 

31 tháng 8 2021

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a: \(\dfrac{-1}{2}+\dfrac{5}{6}+\dfrac{1}{3}\)

\(=\dfrac{-3}{6}+\dfrac{5}{6}+\dfrac{2}{6}\)

\(=\dfrac{4}{6}=\dfrac{2}{3}\)

b: \(\dfrac{-3}{8}+\dfrac{7}{4}-\dfrac{1}{12}\)

\(=\dfrac{-9}{24}+\dfrac{42}{24}-\dfrac{2}{24}\)

\(=\dfrac{31}{24}\)

c: \(\dfrac{3}{5}:\left(\dfrac{1}{4}\cdot\dfrac{7}{5}\right)=\dfrac{3}{4}:\dfrac{7}{20}=\dfrac{3}{4}\cdot\dfrac{20}{7}=\dfrac{15}{7}\)

d: \(\dfrac{10}{11}+\dfrac{4}{11}:4-\dfrac{1}{8}\)

\(=\dfrac{10}{11}+\dfrac{1}{11}-\dfrac{1}{8}=\dfrac{7}{8}\)

6 tháng 9 2021

A = (\(\dfrac{5}{6}\) - \(\dfrac{4}{5}\)) . 1\(\dfrac{1}{5}\) + \(\dfrac{3}{16}\) : (\(\dfrac{-1}{2}\))3

A = \(\dfrac{1}{30}\) . \(\dfrac{6}{5}\) + \(\dfrac{3}{16}\) : \(\dfrac{-1}{8}\)

A = \(\dfrac{1}{25}\) + \(\dfrac{3}{16}\) . \(\dfrac{-8}{1}\)

A = \(\dfrac{1}{25}\) + \(\dfrac{-3}{2}\)

A = \(\dfrac{-73}{50}\)

6 tháng 9 2021

B = \(\dfrac{4}{17}\) . (7\(\dfrac{3}{4}\) - 6\(\dfrac{1}{3}\)) + (5\(\dfrac{3}{4}\) - 6.95) : (-1\(\dfrac{3}{5}\))

B = \(\dfrac{4}{17}\) . \(\dfrac{17}{12}\) + (\(\dfrac{23}{4}\) - \(\dfrac{139}{20}\)) : \(\dfrac{-8}{5}\)

B = \(\dfrac{1}{3}\) + \(\dfrac{-6}{5}\) . \(\dfrac{-5}{8}\)

B = \(\dfrac{13}{12}\)

1 tháng 4 2021

\(\dfrac{2}{3}+\dfrac{1}{5}.\dfrac{10}{7}=\dfrac{2}{3}+\dfrac{10}{35}=\dfrac{70}{105}+\dfrac{30}{105}=\dfrac{100}{105}=\dfrac{50}{21}\)

a) Ta có: \(\dfrac{2}{3}+\dfrac{1}{5}\cdot\dfrac{10}{7}\)

\(=\dfrac{2}{3}+\dfrac{2}{7}\)

\(=\dfrac{14}{21}+\dfrac{6}{21}\)

\(=\dfrac{20}{21}\)

2:

a: =>2/3:x=1,4-2,4=-1

=>x=-2/3

b: =>x/5=25/30-19/30=6/30=1/5

=>x=1

3:

Số học sinh giỏi là 40*1/4=10 bạn

Số học sinh khá là 30*3/5=18 bạn

Số học sinh TB là 30-18=12 bạn

 

5 tháng 5 2021

a) \(\dfrac{-4}{6}\)

b) \(\dfrac{1}{3}\)-\(\dfrac{20}{60}\)

= 0 

c) \(-20^2\)+(\(-50^3\))

= -400 + (-125000)

=-125400

d) \(\dfrac{-2}{7}\)+\(\dfrac{15}{35}\)

\(\dfrac{-10}{35}\)+\(\dfrac{15}{35}\)

\(\dfrac{5}{35}\)=\(\dfrac{1}{7}\)

5 tháng 5 2021

Nhớ tick cho mk nha

HQ
Hà Quang Minh
Giáo viên
5 tháng 10 2023

a) \(\dfrac{7}{8} + \dfrac{7}{8}:\dfrac{1}{8} - \dfrac{1}{2}\)

\(\begin{array}{l} = \dfrac{7}{8} + \dfrac{7}{8}.8 - \dfrac{1}{2}\\ = \dfrac{7}{8}.1 + \dfrac{7}{8}.8 - \dfrac{1}{2}\\ = \left( {\dfrac{7}{8}.1 + \dfrac{7}{8}.8} \right) - \dfrac{1}{2}\\ = \dfrac{7}{8}.\left( {1 + 8} \right) - \dfrac{1}{2} = \dfrac{7}{8}.9 - \dfrac{1}{2}\\ = \dfrac{{63}}{8} - \dfrac{1}{2} = \dfrac{{63}}{8} - \dfrac{4}{8} = \dfrac{{63 - 4}}{8} = \dfrac{{59}}{8}\end{array}\)

b) \(\dfrac{6}{{11}} + \dfrac{{11}}{3}.\dfrac{3}{{22}}\)

\(\begin{array}{l} = \dfrac{6}{{11}} + \dfrac{{11.3}}{{3.22}} = \dfrac{6}{{11}} + \dfrac{1}{2}\\ = \dfrac{{12}}{{22}} + \dfrac{{11}}{{22}} = \dfrac{{12 + 11}}{{22}} = \dfrac{{23}}{{22}}\end{array}\)

HQ
Hà Quang Minh
Giáo viên
5 tháng 10 2023

a) \(\dfrac{{ - 5}}{3} - \dfrac{{ - 7}}{3}\)\( = \dfrac{{ - 5 - \left( { - 7} \right)}}{3} =\dfrac{-5+7}{3} = \dfrac{2}{3}\)

b) \(\dfrac{5}{6} - \dfrac{8}{9}\)\( = \dfrac{{5.3}}{{6.3}} - \dfrac{{8.2}}{{9.2}} = \dfrac{{15}}{{18}} - \dfrac{{16}}{{18}}\)\( = \dfrac{{15 - 16}}{{18}} = \dfrac{{ - 1}}{{18}}\).

HQ
Hà Quang Minh
Giáo viên
5 tháng 10 2023

a) \(\dfrac{6}{{13}}.\dfrac{8}{{7}}.\dfrac{{ - 26}}{3}.\dfrac{{ - 7}}{8}\)

\(\begin{array}{l} = \left( {\dfrac{6}{{13}}.\dfrac{{ - 26}}{3}} \right).\left( {\dfrac{8}{7}.\dfrac{{ - 7}}{8}} \right)\\ = \dfrac{{6.\left( { - 26} \right)}}{{13.3}}.\dfrac{{8.\left( { - 7} \right)}}{{7.8}}\\=  (- 4).\left( { - 1} \right) = 4\end{array}\)

b) \(\dfrac{6}{5}.\dfrac{3}{{13}} - \dfrac{6}{5}.\dfrac{{16}}{{13}}\)

\(\begin{array}{l} = \dfrac{6}{5}.\left( {\dfrac{3}{{13}} - \dfrac{{16}}{{13}}} \right)\\ = \dfrac{6}{5}.\dfrac{{3 - 16}}{{13}}\\ = \dfrac{6}{5}.\dfrac{{-13}}{{13}}\\= \dfrac{6}{5}.\left( { - 1} \right)\\ = \dfrac{{ - 6}}{5}\end{array}\)