a\()\)1/2-1/2:x=3/4

1/2:x=3/4+1/2

1/2:x=5/4

x=5/4*1/2

x=5/8

a,1/2:x=-1/4

x=1/2:-1/4

x=-2

b,Coi 3/5=-3/-5

x=-3+1=-2

c,x=-1,1

\(C=\dfrac{1\dfrac{1}{2}+0,6-\dfrac{3}{7}}{2,5+1-\dfrac{35}{49}}=\dfrac{\dfrac{3}{2}+\dfrac{3}{5}-\dfrac{3}{7}}{\dfrac{5}{2}+\dfrac{5}{5}-\dfrac{5}{7}}=\dfrac{3\left(\dfrac{1}{2}+\dfrac{1}{5}-\dfrac{1}{7}\right)}{5\left(\dfrac{1}{2}+\dfrac{1}{5}-\dfrac{1}{7}\right)}=\dfrac{3}{5}\)

3/5

Ta có: \(A=\dfrac{1-0.5\cdot\left(3.84-2.4\right):0.8}{\dfrac{4}{5}-\left(1\dfrac{1}{3}-2\dfrac{1}{6}\right)-1.5}\)

\(=\dfrac{1-0.5\cdot1.44:0.8}{\dfrac{4}{5}-\left(\dfrac{4}{3}-\dfrac{13}{6}\right)-\dfrac{3}{2}}\)

\(=\dfrac{1-0.9}{\dfrac{4}{5}+\dfrac{5}{6}-\dfrac{3}{2}}=\dfrac{0.1}{\dfrac{2}{15}}=\dfrac{3}{4}\)

Giải:

A=1-0,5.(3,84-2,4):0,8 / 4/5-(1 1/3 - 2 1/6)-1,5

A=1-0,5.1,44:0.8 / 4/5-(4/3-13/6)-3/2

A=1-0.9 / 4/5-(-5/6)-3/2

A=0.1 / 2/15

A= 1/10 : 2/15

A=3/4

Chúc bạn học tốt!

\(\left(x+2,5\right):2\frac{1}{2}-1,5=-1\frac{1}{4}\\ \left(x+2,5\right):2,5=-1\frac{1}{4}+1,5\\ x:2,5+1=\frac{-1}{4}\\ x:\frac{5}{2}=\frac{-5}{4}\\ x=\frac{-1}{2}\)

Bài này dễ nên nãy không có định làm, nhưng mà nghĩ lại thôi làm vậy:Đ

a/ \(\dfrac{x}{-2}=\dfrac{-4}{y}=\dfrac{2}{4}\)

Ta có: \(\dfrac{-4}{y}=\dfrac{2}{4}\Rightarrow y=\dfrac{-4.4}{2}=-8\)

\(\dfrac{x}{-2}=\dfrac{-4}{y}=\dfrac{-4}{-8}=\dfrac{1}{2}\Rightarrow x=\dfrac{-2.1}{2}=-1\)

b/\(\dfrac{2}{x}=\dfrac{y}{-3}\Rightarrow xy=-3.2=-6\)

\(\Rightarrow x;y\inƯ\left(-6\right)=\left\{\pm1;\pm2;\pm3;\pm6\right\}\)

Ta có bảng giá trị của x, y như sau:

c/ \(\dfrac{x+1}{2}=\dfrac{8}{x+1}\Rightarrow\left(x+1\right)^2=2.8=16\)

\(\Rightarrow\left[{}\begin{matrix}\left(x+1\right)^2=4^2\\\left(x+1\right)^2=\left(-4\right)^2\end{matrix}\right.\)\(\Rightarrow\left[{}\begin{matrix}x+1=4\\x+1=-4\end{matrix}\right.\)\(\Rightarrow\left[{}\begin{matrix}x=3\\x=-5\end{matrix}\right.\)

c,(x+1).(x+1)=8.2

(x+1)²=16

⇒x+1=4

⇒x=3

a, \(\dfrac{x-1}{21}\) = \(\dfrac{3}{x+1}\)

   ( x-1)(x+1) = 21.3

    x² + x - x -1 = 63

     x²                = 63 + 1

     x²               = 64

    x = + - 8

b, 2\(\dfrac{1}{2}\)x + x = 2\(\dfrac{1}{17}\)

        x( \(\dfrac{5}{2}\) + 1) = \(\dfrac{35}{17}\)

       x              = \(\dfrac{35}{17}\) : ( \(\dfrac{5}{2}\)+1)

       x             = \(\dfrac{35}{17}\) x \(\dfrac{2}{7}\)

       x            = \(\dfrac{10}{17}\)

c, (x + \(\dfrac{1}{4}\) - \(\dfrac{2}{3}\) ) : ( 2 + \(\dfrac{1}{6}\) - \(\dfrac{1}{4}\)) = \(\dfrac{7}{46}\)

   (x  - \(\dfrac{5}{12}\)):  \(\dfrac{23}{12}\)                     =   \(\dfrac{7}{46}\)

  (x - \(\dfrac{5}{12}\))                               =   \(\dfrac{7}{46}\) x \(\dfrac{23}{12}\)

  x   - \(\dfrac{5}{12}\)                                =    \(\dfrac{7}{12}\)

 x                                            =    \(\dfrac{7}{12}\) + \(\dfrac{5}{12}\)

x                                             =     1

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

   x( \(\dfrac{7}{3}\) - \(\dfrac{7}{4}\)) + \(\dfrac{8}{3}\)      =  \(\dfrac{18}{5}\)

   x\(\dfrac{7}{12}\)                    = \(\dfrac{18}{5}\) - \(\dfrac{8}{3}\)

   x\(\dfrac{7}{12}\)                   = \(\dfrac{14}{15}\)

  x                         = \(\dfrac{14}{15}\) : \(\dfrac{7}{12}\)

 x                          = \(\dfrac{8}{5}\)

\(a,=\dfrac{x^3-\left(x-1\right)\left(x^2+x+1\right)}{1-x}=\dfrac{x^3-x^3+1}{1-x}=\dfrac{1}{1-x}\\ b,=\dfrac{2x+x^2+3x+2+2-x}{\left(x+2\right)^2}=\dfrac{\left(x+2\right)^2}{\left(x+2\right)^2}=1\)

a)

`2/3+5/2-3/4`

`=10/4-3/4+2/3`

`=7/4+2/3`

`=21/12+8/12`

`=29/12`

b)

`2/5xx1/2:1/3`

`=2/10xx3/1`

`=6/10=3/5`

c)

`2/9:2/9xx1/3`

`=2/9xx9/2xx1/3`

`=1xx1/3`

`=1/3`

a, \(\dfrac{2}{3}\) + \(\dfrac{5}{2}\) - \(\dfrac{3}{4}\)

= \(\dfrac{8}{12}\) + \(\dfrac{30}{12}\) - \(\dfrac{9}{12}\)

= \(\dfrac{38-9}{12}\)

= \(\dfrac{29}{12}\)

b, \(\dfrac{2}{5}\) x \(\dfrac{1}{2}\) : \(\dfrac{1}{3}\)

= \(\dfrac{1}{5}\) x \(\dfrac{3}{1}\)

= \(\dfrac{3}{5}\)

c, \(\dfrac{2}{9}\) : \(\dfrac{2}{9}\) x \(\dfrac{1}{3}\)

= 1 x \(\dfrac{1}{3}\)

= \(\dfrac{1}{3}\)

\(=\dfrac{5}{6}+\dfrac{1}{4}=\dfrac{13}{12}\)

\(\dfrac{13}{12}\)

5/6+ 1/4 = 13/12