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\(\frac{15}{31}+\frac{7}{21}+\frac{19}{34}-\frac{20}{15}+\frac{1}{6}\)

\(=\frac{15}{31}+\frac{1}{3}+\frac{19}{34}-\frac{20}{15}+\frac{1}{6}\)

\(=\frac{76}{93}+\frac{19}{34}-\frac{20}{15}+\frac{1}{6}\)

\(=1,37602783-\frac{20}{15}+\frac{1}{6}\)

\(=1,37602783-\frac{4}{3}+\frac{1}{6}\)

\(=0,04269449667+\frac{1}{6}\)

\(=0,2093611633\)

Bài 1 :

\(a,\frac{15}{34}+\frac{7}{21}+\frac{19}{34}-1\frac{7}{21}+2\)

\(=\left(\frac{15}{34}+\frac{19}{34}\right)+\left(\frac{7}{21}-1\frac{7}{21}\right)+2\)

\(=1-1+2\)

\(=2\)

Học tốt

Bài 1 : 

a, 15/34+7/21+19/34-1 7/21+2

 = 15/34+1/3+19/34-4/3+2

 = (15/34+19/34)+(1/3-4/3)+2

 = 1+(-1)+2=0+2=2

\(A=\frac{15}{34}+\frac{7}{21}+\frac{9}{34}-1\frac{15}{17}+\frac{2}{3}\)

   \(=\frac{12}{17}+\frac{1}{3}-\frac{32}{17}+\frac{2}{3}\)

   \(=-\frac{20}{17}+\frac{1}{3}+\frac{2}{3}\)

   \(=-\frac{20}{17}+1\)

   \(=-\frac{3}{17}\)

\(B=16\frac{2}{7}:\left(-\frac{3}{5}\right)-28\frac{2}{7}:\left(-\frac{3}{5}\right)\)

   \(=\left(\frac{114}{7}-\frac{198}{7}\right):\left(-\frac{3}{5}\right)\)

   \(=\left(-12\right):\left(-\frac{3}{5}\right)\)

   \(=20\)

A\(=\frac{15}{34}+\frac{7}{21}+\frac{9}{34}-1\frac{15}{17}+\frac{2}{3}\)

\(=\left(\frac{15}{34}+\frac{9}{34}\right)+\left(\frac{7}{21}+\frac{2}{3}\right)-1\frac{15}{17}\)

\(=\left(\frac{14}{17}-\frac{15}{17}\right)+1-1\)

\(=-\frac{1}{17}\)

\(B=16\frac{2}{7}:\left(-\frac{3}{5}\right)-28\frac{2}{7}:\left(-\frac{3}{5}\right)\)

\(B=-\frac{3}{5}.\left(16\frac{2}{7}-28\frac{2}{7}\right)\)

\(B=-\frac{3}{5}.\left(-12\right)\)

\(B=\frac{36}{5}\)

Hoctot

A=\(\frac{15}{34}\)+ \(\frac{7}{21}\)+  \(\frac{9}{34}\)- 1\(\frac{15}{17}\)+ \(\frac{2}{3}\)

   = ( \(\frac{15}{34}\)+ \(\frac{9}{34}\)) + ( \(\frac{7}{21}\)+ \(\frac{2}{3}\)) - \(\frac{32}{17}\)

  =  \(\frac{24}{34}\)+ ( \(\frac{7}{21}\)+ \(\frac{14}{21}\)) - \(\frac{32}{17}\)

  =\(\frac{12}{17}\)+ \(\frac{21}{21}\)- \(\frac{32}{17}\)

  = ( \(\frac{12}{17}\) - \(\frac{32}{17}\)) +1

  =\(\frac{-20}{17}\)+ \(\frac{17}{17}\)

  = \(\frac{-3}{17}\)

Tính:

b) \(\left(-2\right)^3.\left(\frac{3}{4}-0,25\right):\left(2\frac{1}{4}-1\frac{1}{6}\right)\)

\(=\left(-2\right)^3.\left(\frac{3}{4}-\frac{1}{4}\right):\left(\frac{9}{4}-\frac{7}{6}\right)\)

\(=\left(-8\right).\frac{1}{2}:\frac{13}{12}\)

\(=\left(-4\right):\frac{13}{12}\)

\(=-\frac{48}{13}.\)

Tìm x

a) \(4\frac{1}{3}:\frac{x}{4}=6:0,3\)

⇒ \(\frac{13}{3}:\frac{x}{4}=20\)

⇒ \(\frac{x}{4}=\frac{13}{3}:20\)

⇒ \(\frac{x}{4}=\frac{13}{60}\)

⇒ \(x.60=4.13\)

⇒ \(x.60=52\)

⇒ \(x=52:60\)

⇒ \(x=\frac{13}{15}\)

Vậy \(x=\frac{13}{15}.\)

b) \(\left(2^3:4\right).2^{x+1}=64\)

⇒ \(\left(8:4\right).2^{x+1}=64\)

⇒ \(2.2^{x+1}=64\)

⇒ \(2^{x+1}=64:2\)

⇒ \(2^{x+1}=32\)

⇒ \(2^{x+1}=2^5\)

⇒ \(x+1=5\)

⇒ \(x=5-1\)

⇒ \(x=4\)

Vậy \(x=4.\)

Chúc bạn học tốt!

a: \(A=\left(\dfrac{15}{34}+\dfrac{9}{34}-1-\dfrac{15}{17}\right)+\left(\dfrac{1}{3}+\dfrac{2}{3}\right)\)

\(=\left(\dfrac{12}{17}-1-\dfrac{15}{17}\right)+1\)

\(=\dfrac{-20}{17}+1=\dfrac{-3}{17}\)

b: \(B=\dfrac{-5}{3}\cdot16\dfrac{2}{7}-\dfrac{-5}{3}\cdot28\dfrac{2}{7}\)

\(=\dfrac{-5}{3}\left(16+\dfrac{2}{7}-28-\dfrac{2}{7}\right)=\dfrac{-5}{3}\cdot\left(-12\right)=20\)

c: \(C=25\cdot\dfrac{-1}{27}+\dfrac{1}{5}-2\cdot\dfrac{1}{4}-\dfrac{1}{2}\)

\(=\dfrac{-25}{27}+\dfrac{1}{5}-1\)

\(=\dfrac{-125+27-135}{135}=\dfrac{-233}{135}\)