a) \(...=-\dfrac{1}{4}.\dfrac{4}{17}.\left(-\dfrac{63}{21}\right).\left(-\dfrac{7}{12}\right)\)

\(=-\dfrac{1}{17}.\dfrac{63}{21}.\dfrac{7}{12}\)

\(=-\dfrac{7}{68}\)

b) \(...=-\dfrac{2}{5}.\dfrac{4}{15}-\dfrac{3}{10}.\dfrac{4}{15}\)

\(=\dfrac{4}{15}\left(-\dfrac{2}{5}-\dfrac{3}{10}\right)\)

\(=\dfrac{4}{15}\left(-\dfrac{4}{10}-\dfrac{3}{10}\right)\)

\(=\dfrac{4}{15}.\left(-\dfrac{7}{10}\right)=-\dfrac{14}{75}\)

c) \(...=21-\dfrac{15}{4}:\left(\dfrac{9}{24}-\dfrac{4}{24}\right)\)

\(=21-\dfrac{15}{4}:\dfrac{5}{24}\)

\(=21-\dfrac{15}{4}.\dfrac{24}{5}\)

\(=21-3.6=3\)

d) \(...=\left(-\dfrac{3}{4}+\dfrac{2}{5}\right).\dfrac{7}{3}+\left(\dfrac{3}{5}-\dfrac{1}{4}\right).\dfrac{7}{3}\)

\(=\dfrac{7}{3}\left(-\dfrac{3}{4}+\dfrac{2}{5}+\dfrac{3}{5}-\dfrac{1}{4}\right)\)

\(=\dfrac{7}{3}\left(-\dfrac{3}{4}-\dfrac{1}{4}+\dfrac{2}{5}+\dfrac{3}{5}\right)\)

\(=\dfrac{7}{3}\left(-1+1\right)=0\)

`@` `\text {Ans}`

`\downarrow`

`1/3+6/9+4/5+5/25`

`= 1/3+2/3+4/5+1/5`

`= 1+1`

`= 2`

`4/7*2/5+4/7*3/5-1/7`

`= 4/7*(2/5+3/5)-1/7`

`= 4/7*1-1/7`

`= 4/7-1/7=3/7`

.....................................................

4/5(15+2/3)-4/5(20+2/3)=188/15-6/155=1162/93

\(\frac{4}{5}\left(15+\frac{2}{3}\right)-\frac{4}{5}\left(20+\frac{2}{3}\right)\)

\(=\frac{4}{5}\left[\left(15+\frac{2}{3}\right)-\left(20+\frac{2}{3}\right)\right]\)

\(=\frac{4}{5}.\left(15+\frac{2}{3}-20-\frac{2}{3}\right)\)

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

\(=-4\)

\(\dfrac{3}{2}\)(\(x\) - \(\dfrac{5}{3}\)) - \(\dfrac{4}{5}\) = \(x\) + 1

\(\dfrac{3}{2}\) \(x\) - \(\dfrac{15}{6}\) - \(\dfrac{4}{5}\) = \(x\) + 1

\(\dfrac{3}{2}\)\(x\) - \(x\)          = 1 + \(\dfrac{15}{6}\) + \(\dfrac{4}{5}\)

\(\dfrac{1}{2}\)\(x\)                 =\(\dfrac{43}{10}\)

    \(x\)                 = \(\dfrac{43}{10}\) \(\times\) 2

     \(x\)                = \(\dfrac{43}{5}\)

\(\dfrac{3}{2}\left(x-\dfrac{5}{3}\right)-\dfrac{4}{5}=x+1\\ \Rightarrow\dfrac{3.\left(x-\dfrac{5}{3}\right)}{2}-\dfrac{4}{5}=x+1\\ \Rightarrow\dfrac{3x-5}{2}-\dfrac{4}{5}=x+1\Rightarrow\dfrac{5\left(3x-5\right)}{10}-\dfrac{8}{10}=x+1\\ \Rightarrow\dfrac{15x-33}{10}=x+1\\ \Rightarrow\dfrac{15x-33}{10}-x=x+1\\ \Rightarrow\dfrac{15x-33}{10}=x+1-x\\ \Rightarrow5x-33=10\\ \Rightarrow5x=10+33\\\Rightarrow5x=43\\ \Rightarrow x=\dfrac{43}{5} \)

\(\dfrac{3}{2}\times\left(x-\dfrac{5}{3}\right)-\dfrac{4}{5}=x+1\)

\(\Leftrightarrow\dfrac{3}{2}\times x-\dfrac{5}{2}-\dfrac{4}{5}=x+1\)

\(\Leftrightarrow\dfrac{3}{2}\times x-x=1+\dfrac{5}{2}+\dfrac{4}{5}\)

\(\Leftrightarrow\dfrac{1}{2}\times x=\dfrac{43}{10}\)

\(\Leftrightarrow x=\dfrac{43}{10}\div\dfrac{1}{2}\)

\(\Leftrightarrow x=\dfrac{43}{5}\)

a,=14/7+4/7

=18/7

2+4/7=14/7+4/7=18/7

\(\dfrac{18}{7}\)

x : 4/5 = 3/4

x         = 3/4 x 4/5 

x         = 3/5

HT

x:4/5=3/4 x=3/4x4/5 x=12/20=3/5

3/4 nha

Lỗi hình ảnh rồi bạn nhé!

(3/5+2/5)+(4/9+5/9)=1+1=2

(5/4+3/4)+(3/8+5/8)=8/4+1=8/4  

mik mới lớp 5 =]]

nên ko biết =]]]]]

=]]]]]]]]

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