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\(\frac{19}{15}+\frac{31}{23}-\frac{4}{15}-\frac{8}{23}\)
\(=\left(\frac{19}{15}-\frac{4}{15}\right)+\left(\frac{31}{23}-\frac{8}{23}\right)\)
\(=\frac{15}{15}+\frac{23}{23}\)
\(=1+1=2\)
\(\frac{19}{15}+\frac{31}{23}-\frac{14}{15}-\frac{8}{23}\)
\(=\frac{19}{15}-\frac{4}{15}+\frac{31}{23}-\frac{8}{23}\)
\(=1+1=2\)
chúc bạn học giỏi
a) \(\dfrac{16}{15}+\dfrac{7}{15}+\dfrac{4}{15}=\left(\dfrac{16}{15}+\dfrac{4}{15}\right)+\dfrac{7}{15}=\dfrac{20}{15}+\dfrac{7}{15}=\dfrac{27}{15}\)
b) \(\dfrac{5}{17}+\dfrac{7}{17}+\dfrac{13}{17}=\dfrac{5}{17}+\left(\dfrac{7}{17}+\dfrac{13}{17}\right)=\dfrac{5}{17}+\dfrac{20}{17}=\dfrac{25}{17}\)
1.
=2/5 x 12/3 + 2/5 x 15/3 + 2/5 x 1
= 2/5 x (12/3 + 15/3 + 1)
=2/5 x 1
=2/5
2.a=1;2
\(15x\frac{2121}{4343}+15x\frac{222222}{434343}\)
\(=15x\frac{21}{43}+15x\frac{22}{43}\)
\(=15x\left(\frac{21}{43}+\frac{22}{43}\right)\)
\(=15x1\)
\(=15\)
= 15 x 21/43 + 15x 22/43
= 15 x (21/43 + 22/43)
= 15 x 1 =15
\(a,\dfrac{5}{13}\times\dfrac{4}{15}\times13=\dfrac{5\times4\times13}{13\times5\times3}=\dfrac{4}{3}\\ b,\left(\dfrac{3}{7}+\dfrac{5}{2}\right)\times\dfrac{7}{5}=\dfrac{3}{7}\times\dfrac{7}{5}+\dfrac{5}{2}\times\dfrac{7}{5}=\dfrac{3}{5}+\dfrac{7}{2}=\dfrac{6}{10}+\dfrac{35}{10}=\dfrac{41}{10}\\ c,\dfrac{1}{5}\times\dfrac{11}{18}+\dfrac{11}{18}\times\dfrac{3}{5}=\dfrac{11}{18}\times\left(\dfrac{1}{5}+\dfrac{3}{5}\right)=\dfrac{11}{18}\times\dfrac{4}{5}=\dfrac{22}{45}\)
60x [7/12+4/15]
60x153/180
=9180/180
b 1/2x2/3x3/4x4/5x5/6x6/7x7/8x8/9=40320/4032
\(\frac{8}{15}:\frac{2}{11}+\frac{7}{15}:\frac{2}{11}\)
\(=\left(\frac{8}{15}+\frac{7}{15}\right):\frac{2}{11}\)
\(=1:\frac{2}{11}\)
\(=\frac{11}{2}\)
\(\frac{3}{4}.\frac{8}{9}.\frac{15}{16}.\frac{24}{25}.\frac{35}{36}\)
\(=\frac{3.2.4.3.5.4.6.5.7}{2.2.3.3.4.4.5.5.6.6}=\frac{7}{2.6}\)
\(=\frac{7}{12}\)
\(=\frac{1\cdot3\cdot2\cdot4\cdot3\cdot5\cdot4\cdot6\cdot5\cdot7}{2\cdot2\cdot3\cdot3\cdot4\cdot4\cdot5\cdot5\cdot6\cdot6}\)
\(=\frac{1\cdot7}{2\cdot6}\)
\(=\frac{7}{12}\)
\(3\times\dfrac{4}{15}+2\times\dfrac{4}{15}-5\times\dfrac{4}{15}\\ =\dfrac{4}{15}\times\left(3+2-5\right)\\ =\dfrac{4}{15}\times0\\ =0\)