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\(2\frac{3}{13}\cdot\frac{26}{58}\cdot4\cdot2\frac{15}{24}\cdot\frac{8}{21}=\frac{29}{13}\cdot\frac{26}{58}\cdot4\cdot\frac{21}{8}\cdot\frac{8}{21}=\frac{29\cdot26\cdot4\cdot21\cdot8}{13\cdot58\cdot8\cdot21}=\frac{1\cdot2\cdot4\cdot1\cdot1}{1\cdot2\cdot1\cdot1}=\frac{1\cdot4}{1}=4\)
\(=\dfrac{29}{13}\cdot\dfrac{13}{29}\cdot4\cdot\dfrac{21}{8}\cdot\dfrac{8}{21}=4\)
\(2\frac{3}{13}.\frac{27}{58}.2\frac{15}{24}.\frac{8}{21}:\frac{3}{7}=\frac{29}{13}.\frac{27}{58}.\frac{63}{24}.\frac{8}{21}:\frac{3}{7}=\frac{27}{26}.\frac{63}{24}.\frac{8}{21}:\frac{3}{7}=\frac{567}{208}.\frac{8}{21}:\frac{3}{7}=\frac{27}{26}:\frac{3}{7}=\frac{63}{26}\)
= \(\frac{13}{45}x\left(\frac{15}{26}-1\frac{1}{26}+\frac{11}{26}\right)=\frac{13}{45}x\left(\frac{15}{26}-\frac{27}{26}+\frac{11}{26}\right)=\frac{13}{45}x\left(\frac{27}{26}-\frac{27}{26}\right)=\frac{13}{45}x0=0\)
a) \(x\cdot\frac{1}{2}+x\cdot\frac{1}{4}+x\cdot\frac{1}{8}=\frac{21}{24}\)
\(x\cdot\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}\right)=\frac{7}{8}\)
\(x\cdot\frac{7}{8}=\frac{7}{8}\)
\(\Rightarrow x=\frac{7}{8}\div\frac{7}{8}=1\)
b) \(\left(x+4\right)+\left(x+9\right)+\left(x+14\right)+.....+\left(x+44\right)+\left(x+49\right)=1430\)
\(\left(x+x+x+....+x+x\right)+\left(4+9+14+...+44+49\right)=1430\)
\(10x+265=1430\)
\(10x=1430-265\)
\(10x=1165\)
\(\Rightarrow x=\frac{1165}{10}=116,5\)
c) \(x\cdot0,25-0,5=1\)
\(x\cdot0,25=1+0,5\)
\(x\cdot0,25=1,5\)
\(\Rightarrow x=1,5\div0,25=6\)
{9/5-3/5} : {15/3-11/5}
6/5:14/5
6/5x5/14=3/7
Câu 2:
{2/1x3+2/3x5+...+2/19x21} x{1/28-5/2x1/70}
{2/1x3+2/3x5+...+2/19x21} x{1/28-1/28}
{2/1x3+2/3x5+...+2/19x21} x0=0
\(2\times\frac{3}{13}\times\frac{26}{58}\times4\times2\frac{15}{24}\times\frac{8}{21}\)
\(=\left(2\times4\right)\times\left(\frac{3}{13}\times\frac{26}{58}\times\frac{63}{24}\times\frac{8}{21}\right)\)
\(=8\times\left(\frac{3\times26\times63\times8}{13\times58\times24\times21}\right)\)
\(=8\times\left(\frac{3\times13\times2\times7\times3\times3\times8}{13\times29\times2\times3\times8\times7\times3}\right)\)
\(=8\times\left(\frac{2\times3\times8}{29}\right)\)
\(=8\times\left(\frac{48}{29}\right)\)
\(=\frac{8\times48}{29}\)
\(=\frac{384}{29}=13\frac{7}{29}\)