3 x 23/8
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a,
23 x (7 - 4) = 23 x 3 = 69
23 x 7 - 23 x 4 = 161 - 92 = 69
Ta có: 23 x (7 - 4) = 23 x 7 - 23 x 4
b,
(8 - 3) x 9 = 5 x 9 = 45
8 x 9 - 3 x 9 = 72 - 27 = 45
Ta có: (8 - 3) x 9 = 8 x 9 - 3 x 9
\(A=\frac{3}{2}\times5+\frac{3}{5}\times8+\frac{3}{8}\times11+.....+\frac{3}{20}\times23+\frac{3}{23}\times26\)
\(A=\frac{3}{2}\times\frac{5}{1}+\frac{3}{5}\times\frac{8}{1}+\frac{3}{8}\times\frac{11}{1}+.....+\frac{3}{20}\times\frac{23}{1}+\frac{3}{23}\times\frac{26}{1}\)
\(A=\left(\frac{3}{2}\times\frac{5}{1}+\frac{3}{23}\times\frac{26}{1}\right)+.....+\left(\frac{3}{11}\times\frac{14}{1}+\frac{3}{14}\times\frac{17}{1}\right)\)CÓ 8 CẶP
\(A=\left(\frac{15}{2}+\frac{68}{23}\right)+.....+\left(\frac{42}{11}+\frac{51}{14}\right)\)
\(A=\left(\frac{15}{2}+\frac{68}{23}\right)+.....+\left(\frac{42}{11}+\frac{51}{14}\right)\)
CÒN LẠI TỰ GIẢI NHA
\(\dfrac{-9}{46}-4\dfrac{1}{23}:\left(3\dfrac{1}{4}-x:\dfrac{3}{5}\right)+2\dfrac{8}{23}=1\)
\(\dfrac{-9}{46}+2\dfrac{8}{23}-4\dfrac{1}{23}:\left(3\dfrac{1}{4}-x:\dfrac{3}{5}\right)=1\)
\(\dfrac{-9}{46}+\dfrac{54}{23}-\dfrac{93}{23}:\left(\dfrac{13}{4}-x:\dfrac{3}{5}\right)=1\)
\(\dfrac{-9}{46}+\dfrac{108}{46}-\dfrac{93}{23}:\left(\dfrac{13}{4}-x:\dfrac{3}{5}\right)=1\)
\(\dfrac{99}{46}-\dfrac{93}{23}:\left(\dfrac{13}{4}-x:\dfrac{3}{5}\right)=1\)
\(\dfrac{93}{23}:\left(\dfrac{13}{4}-x:\dfrac{3}{5}\right)=\dfrac{99}{46}-1\)
\(\dfrac{93}{23}:\left(\dfrac{13}{4}-x:\dfrac{3}{5}\right)=\dfrac{99}{46}-\dfrac{46}{46}\)
\(\dfrac{93}{23}:\left(\dfrac{13}{4}-x:\dfrac{3}{5}\right)=\dfrac{53}{46}\)
\(\dfrac{13}{4}-x:\dfrac{3}{5}=\dfrac{93}{23}:\dfrac{53}{46}\)
\(\dfrac{13}{4}-x:\dfrac{3}{5}=\dfrac{93}{23}\cdot\dfrac{46}{53}\)
\(\dfrac{13}{4}-x:\dfrac{3}{5}=\dfrac{186}{53}\)
\(x:\dfrac{3}{5}=\dfrac{13}{4}-\dfrac{186}{53}\)
\(x:\dfrac{3}{5}=\dfrac{689}{212}-\dfrac{744}{212}\)
\(x:\dfrac{3}{5}=\dfrac{-55}{212}\)
\(x=\dfrac{-55}{212}\cdot\dfrac{3}{5}\)
\(x=\dfrac{-33}{212}\)
Vậy \(x=\dfrac{-33}{212}\).
2: \(=\dfrac{-2}{75}+\dfrac{5}{39}=\dfrac{33}{325}\)
3: \(=\dfrac{6}{11}\left(\dfrac{4}{9}+\dfrac{5}{9}\right)=\dfrac{6}{11}\)
4: \(=\dfrac{7}{19}\left(\dfrac{5}{13}+\dfrac{8}{13}-1\right)=-2\cdot\dfrac{7}{19}=-\dfrac{14}{19}\)
5: \(=\dfrac{2}{7}\left(\dfrac{4}{23}-\dfrac{27}{23}+1\right)=0\)
6: \(=\dfrac{3}{8}\left(\dfrac{3}{7}+\dfrac{4}{7}\right)+\dfrac{11}{8}=\dfrac{3}{8}+\dfrac{11}{8}=\dfrac{14}{8}=\dfrac{7}{4}\)
-23(x - 23) + 8(8 - x) = 23
=> -23x + 529 + 64 - 8x = 23
=> (-23x - 8x) + (529 + 64) = 23
=> -31x + 593 = 23
=> -31x = -570
=> x = 570/31
a) Ta có: \(\frac{7}{8}+\frac{15}{23}+\frac{1}{8}+\left(-\frac{15}{23}\right)+\frac{1}{3}\)
\(=\left(\frac{7}{8}+\frac{1}{8}\right)+\left(\frac{15}{23}-\frac{15}{23}\right)+\frac{1}{3}\)
\(=1+\frac{1}{3}=\frac{4}{3}\)
b) Ta có: \(\frac{3-\frac{2}{3}}{\frac{1}{3}-3}\)
\(=\left(3-\frac{2}{3}\right)\cdot\frac{1}{\frac{1}{3}-3}=\left(3-\frac{2}{3}\right)\cdot\frac{1}{-\frac{8}{3}}\)
\(=\left(3-\frac{2}{3}\right)\cdot\frac{-3}{8}\)
\(=-\frac{9}{8}+\frac{1}{4}=\frac{-9}{8}+\frac{2}{8}=-\frac{7}{8}\)
c) Ta có: \(8\cdot\left(-\frac{1}{2}\right)^3+3\cdot\left(-\frac{1}{2}\right)^2-0,75\)
\(=8\cdot\frac{-1}{8}+3\cdot\frac{1}{4}-\frac{3}{4}\)
\(=-1\)
3 \(\times\) \(\dfrac{23}{8}\) = \(\dfrac{3\times23}{8}\) = \(\dfrac{69}{8}\)
Chúc cậu học tốt nhé !!
3 × 23/8 = 69/8