Bn ghi 'Tham khảo' vào aj!

Ta có : 1 nghìn = 10 trăm.

`=>`4 nghìn = 4 × 10 = 40 trăm

Vậy...

$\color{#B0E0E6}{\text{@456 × @Aoi}}$

Bạn Kudo Shinichi@ , bạn có thể giải rõ ra được không?

Sửa đề :\(1,-\dfrac{5}{9}\times\dfrac{2}{13}+-\dfrac{5}{13}\times\dfrac{11}{9}-\dfrac{4}{9}\)

\(=-\dfrac{5}{9}\times\dfrac{2}{13}+-\dfrac{5}{9}\times\dfrac{11}{13}-\dfrac{4}{9}\)

\(=-\dfrac{5}{9}\times\left(\dfrac{2}{13}+\dfrac{11}{13}\right)-\dfrac{4}{9}\)

\(=-\dfrac{5}{9}\times1-\dfrac{4}{9}\)

\(=-1\)

\(2,\dfrac{4}{9}\times\left(\dfrac{5}{7}+\dfrac{2}{5}\right)-\dfrac{4}{9}\times\left(-\dfrac{2}{7}+\dfrac{7}{5}\right)\)

\(=\dfrac{4}{9}\times\left[\left(\dfrac{5}{7}+\dfrac{2}{5}\right)-\left(-\dfrac{2}{7}+\dfrac{7}{5}\right)\right]\)

\(=\dfrac{4}{9}\times\left[\dfrac{5}{7}+\dfrac{2}{5}+\dfrac{2}{7}-\dfrac{7}{5}\right]\)

\(=\dfrac{4}{9}\times\left[\left(\dfrac{5}{7}+\dfrac{2}{7}\right)+\left(\dfrac{2}{5}-\dfrac{7}{5}\right)\right]\)

\(=\dfrac{4}{9}\times\left[1+-1\right]\)

\(=\dfrac{4}{9}\times0=0\)

\(3,\left(\dfrac{5}{4}+\dfrac{3}{4}\right)\times\dfrac{4}{7}+\left(\dfrac{3}{4}+\dfrac{9}{4}\right)\times\dfrac{4}{7}\)

\(=\left[\left(\dfrac{5}{4}+\dfrac{3}{4}\right)+\left(\dfrac{3}{4}+\dfrac{9}{4}\right)\right]\times\dfrac{4}{7}\)

\(=\left[\dfrac{5}{4}+\dfrac{3}{4}+\dfrac{3}{4}+\dfrac{9}{4}\right]\times\dfrac{4}{7}\)

\(=\left[\left(\dfrac{5}{4}+\dfrac{9}{4}\right)+\left(\dfrac{3}{4}+\dfrac{3}{4}\right)\right]\times\dfrac{4}{7}\)

\(=\left[\dfrac{7}{2}+\dfrac{3}{2}\right]\times\dfrac{4}{7}\)

\(=5\times\dfrac{4}{7}\)

\(=\dfrac{20}{7}\)

$\color{#87CEFA}{\text{@Aoi}}$$\color{#B0E0E6}{\text{@456}}$

Uả cái này trong bài văn số 328 mà!

\(1,-\dfrac{7}{11}\times\dfrac{11}{19}+\dfrac{8}{19}\times-\dfrac{7}{11}+-\dfrac{4}{11}\)

\(=-\dfrac{7}{11}\times\left(\dfrac{11}{19}+\dfrac{8}{19}\right)+-\dfrac{4}{11}\)

\(=-\dfrac{7}{11}\times1+-\dfrac{4}{11}\)

\(=-\dfrac{7}{11}+-\dfrac{4}{11}\)

\(=-1\)

\(2,-\dfrac{3}{5}\times\dfrac{2}{7}+-\dfrac{3}{7}\times\dfrac{3}{5}+-\dfrac{3}{7}\)

\(=\) \(\dfrac{3}{5}\times-\dfrac{2}{7}+-\dfrac{3}{7}\times\dfrac{3}{5}+-\dfrac{3}{7}\)
\(=\dfrac{3}{5}\times\left(-\dfrac{2}{7}+-\dfrac{3}{7}\right)+-\dfrac{3}{7}\)

\(=\dfrac{3}{5}\times-\dfrac{5}{7}+-\dfrac{3}{7}\)

\(=-\dfrac{3}{7}+-\dfrac{3}{7}\)

\(=-\dfrac{6}{7}\)