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Bài 1:
0,5\(x\) - \(\dfrac{2}{3}\)\(x\) = \(\dfrac{7}{12}\)
\(\dfrac{1}{2}\)\(x\) - \(\dfrac{2}{3}x\) = \(\dfrac{7}{12}\)
(\(\dfrac{1}{2}-\dfrac{2}{3}\))\(x\) = \(\dfrac{7}{12}\)
- \(\dfrac{1}{6}\)\(x\) = \(\dfrac{7}{12}\)
\(x\) = \(\dfrac{7}{12}\) : (- \(\dfrac{1}{6}\))
\(x\) = - \(\dfrac{7}{2}\)
Vậy \(x\) = - \(\dfrac{7}{2}\)
1:
a: \(=\dfrac{-4}{7}+\dfrac{4}{7}+\dfrac{3}{7}-\dfrac{23}{34}-\dfrac{4}{5}=\dfrac{3}{7}-\dfrac{23}{34}-\dfrac{4}{5}=-\dfrac{1247}{1190}\)
b:
Sửa đề: \(\dfrac{-5}{13}+\dfrac{4}{19}+\dfrac{-8}{13}+\dfrac{15}{19}+\dfrac{45}{6}\)
\(=\dfrac{-5}{13}-\dfrac{8}{13}+\dfrac{4}{19}+\dfrac{15}{19}+\dfrac{45}{6}=\dfrac{9}{2}\)
G=\(\frac{3}{2.5}+\frac{3}{5.7}+\frac{3}{7.9}+...+\frac{3}{2015.2017}\)
G=\(3.\left(\frac{1}{2.5}+\frac{1}{5.7}+\frac{1}{7.9}+...+\frac{1}{2015.2017}\right)\)
G=\(3.\left(\frac{1}{2}.\frac{1}{5}+\frac{1}{5}.\frac{1}{7}+\frac{1}{7}.\frac{1}{9}+...+\frac{1}{2013}.\frac{1}{2015}+\frac{1}{2015}.\frac{1}{2017}\right)\)
G=\(3.\left(\frac{1}{2}+\frac{1}{2017}\right)\)
G=1.5
Anh ko bik có đúng ko nữa lâu quá rồi. Em thông cảm nhé
1)a, \(0,5x-\frac{2}{3}x=\frac{7}{12}\) b) \(x:4\frac{1}{3}=-\frac{2}{5}\)
\(x\left(0,5-\frac{2}{3}\right)=\frac{7}{12}\) \(x=-\frac{2}{5}.4\frac{1}{3}\)
\(-\frac{1}{6}x=\frac{7}{12}\) \(x=-\frac{26}{15}\)
\(x=\frac{-7}{2}\)
c) \(\left(\frac{3x}{7}+1\right):\left(-4\right)=-\frac{1}{28}\) d) \(x+30\%x=-1,3\)
\(\frac{3x}{7}+1=-\frac{1}{28}.\left(-4\right)\) \(x\left(1+30\%\right)=-1,3\)
\(\frac{3x}{7}+1=\frac{1}{7}\) \(1,3x=-1,3\)
\(\frac{3x}{7}=-\frac{6}{7}\) \(x=-1,3:1,3\)
\(x=-6.7:7:3\) \(x=-1\)
\(x=-2\)
Bài 2:
\(\frac{3}{5.7}+\frac{3}{7.9}+...+\frac{3}{2019.2021}=\frac{3}{2}\left(\frac{2}{5.7}+\frac{2}{7.9}+...+\frac{2}{2019.2021}\right)\)
\(=\frac{3}{2}\left(\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{2019}-\frac{1}{2021}\right)\)
\(=\frac{3}{2}.\left(\frac{1}{5}-\frac{1}{2021}\right)\)
\(=\frac{3}{2}.\frac{2016}{10105}\)
\(=\frac{3024}{10105}\)
2:
a: x=2,4-0,4=2
b: =>2x=-1,5+0,8=-0,7
=>x=-0,35
c: =>x-16=-15
=>x=1
a) \(\dfrac{5}{24}+x=\dfrac{7}{12}\)
<=> \(x=\dfrac{7}{12}-\dfrac{5}{24}=\dfrac{14}{24}-\dfrac{5}{24}=\dfrac{9}{24}=\dfrac{3}{8}\)
b) \(x-\dfrac{3}{4}=\dfrac{1}{2}\)
<=> \(x=\dfrac{1}{2}+\dfrac{3}{4}=\dfrac{2}{4}+\dfrac{3}{4}=\dfrac{5}{4}\)
c) bn ghi rõ đề chút