-5/9 . 13/28 - 13/28 . 4/9

= 13/28 . (-5/9 - 4/9)

= 13/28 . (-1)

= -13/28

`-5/9 xx 13/28 - 13/28 xx 4/9`

`= 13/28 xx ((-5)/9 - 4/9)`

`= 13/28 xx (-1)`

`= -13/28`

a)

 \(\frac{{28}}{9} \cdot 0,7 + \frac{{28}}{9} \cdot 0,5 = \frac{{28}}{9}.\left( {0,7 + 0,5} \right)\)

b)

\(\begin{array}{l}\frac{{36}}{{13}}:4 + \frac{{36}}{{13}}:9\\ = \frac{{36}}{{13}}.\frac{1}{4} + \frac{{36}}{{13}}.\frac{1}{9}\\ = \frac{{36}}{{13}}.\left( {\frac{1}{4} + \frac{1}{9}} \right)\\ = \frac{{36}}{{13}}.\frac{{13}}{{36}} = 1\end{array}\)

 \(\begin{array}{l}\frac{{36}}{{13}}:(4 + 9)\\ = \frac{{36}}{{13}}:13\\ = \frac{{36}}{{13}}.\frac{1}{{13}}\\ = \frac{{36}}{{169}}\end{array}\)

Suy ra \(\frac{{36}}{{13}}:4 + \frac{{36}}{{13}}:9\) \( \ne \) \(\frac{{36}}{{13}}:(4 + 9)\).

\(A=\frac{13}{28}\left(-\frac{5}{9}-\frac{4}{9}\right)=\frac{13}{28}\left(-\frac{9}{9}\right)=\frac{13}{28}\left(-1\right)\)

=> \(A=-\frac{13}{28}\)

A= -5/9x 13/28- 13/28x 4/9

  =13/28x (-5/9- 4/9)

  =13/28x (-1)

  =-13/28

A=(-5/9-4/9)*13/28

A=-1*13/28

A=-13/28

\(\frac{-5}{9}.\frac{13}{28}-\frac{13}{28}.\frac{4}{9}\)

\(=\frac{13}{28}.\left(\frac{-5}{9}-\frac{4}{9}\right)\)

\(=\frac{13}{28}.\left(-1\right)\)

\(=\frac{-13}{28}\)

=13/28.(-5/9-4/9)

=13/28.(-1)

=-13/28

\(\frac{-5}{9}.\frac{13}{28}-\frac{13}{28}.\frac{4}{9}\)

\(=\frac{13}{28}.\left[\frac{\left(-5\right)}{9}+\frac{4}{9}\right]\)

\(=\frac{13}{28}.\left(-1\right)\)

\(=-\frac{13}{28}\)

13/28nhan(5/9+4/9)

13/28nhan1=13/28

5/9x13/28+13/28x4/9

=(5/9+4/9)x13/28

=1x13/28

=13/28

5/9  x 13/28 +13/28 x 4/9 

= 13/28 x ( 5/9 + 4/9 )

= 13/28 x 1

= 13/28

Phương pháp giải:

- Thực hiện phép tính nhân hoặc chia rồi cộng hoặc trừ với số còn lại. 

- Trình bày lần lượt theo thứ tự các phép tính vừa tính.

Lời giải chi tiết:

5 × 3 + 5 = 15 + 5 = 20

28 : 4 + 13 = 7 + 13 = 20

4 × 9 − 16 = 36 − 16 = 20

Bài làm

a) \(\left(\frac{3}{8}+\frac{-1}{4}+\frac{5}{12}\right):\frac{2}{3}\)

\(=\left(\frac{9}{24}+\frac{-6}{24}+\frac{10}{24}\right).\frac{3}{2}\)

\(=\frac{13}{24}.\frac{3}{2}\)

\(=\frac{39}{48}\)

b) \(\frac{-5}{7}.\frac{2}{11}+\frac{-5}{7}.\frac{9}{11}+1\frac{5}{7}\)

\(=-\frac{5}{7}.\left(\frac{2}{11}+\frac{9}{11}\right)+\frac{12}{7}\)

\(=-\frac{5}{7}.1+\frac{12}{7}\)

\(=\frac{7}{7}\)

\(=1\)

c) \(0,25:\left(10,3-9,8\right)-\frac{3}{4}\)

\(=\frac{25}{100}:\left(0,5\right)-\frac{3}{4}\)

\(=\frac{5}{4}:\frac{1}{2}-\frac{3}{4}\)

\(=\frac{5}{4}.2-\frac{3}{4}\)

\(=\frac{5}{2}-\frac{3}{4}\)

\(=\frac{10}{4}-\frac{3}{4}=\frac{7}{4}\)

d) \(-\frac{5}{9}.\frac{13}{28}-\frac{13}{28}.\frac{4}{9}\)

\(=-\frac{13}{28}\left(\frac{5}{9}+\frac{4}{9}\right)\)

\(=-\frac{13}{28}.\frac{9}{9}\)

\(=-\frac{13}{28}.1\)

\(=-\frac{13}{28}\)

a) S

b) Đ

c) Đ

d) S

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