=12/37 nha 

nhớ cho mình nha!

x=- 100

1a) -54 . 76 + 12 .(-76) + 76.(-34)

= (-54 - 12 - 34).76

= -100 . 76

= -176

b) 37.(63 - 24) - 63.(24 + 37)

= 37 . 63 - 37 . 24 - 63.24 - 63 . 37

= (37.63 - 63.37) - (37 + 63) . 24

= 0 - 100 . 24

= - 2400

2a) x + (-27) = -23 - x

=> x + x = -23 + 27

=> 2x = 4

=> x = 4 : 2

=> x = 2

b) xy + 2x - y = 15

=> x(y + 2) - y = 15

=> x(y + 2) - (y + 2) = 13

=> (x - 1)(y + 2) = 13 = 1 . 13 = 13 . 1

Lập bảng :

Vậy ...

 x  - 17 = 2 x 17 x 5 

=> X -  17  =  170

=>  x   =  187

 49 - x = 21 x  63 + 37 x 3 x 7

=> 49 - x  =  21( 63 + 37)

=>  49 - x  =  2100

=>  x  =  -  2051

2x + 3x = 15

=>  5x  =    15

=>   x  =  3

không ghi lại đề nha !

a ) = 2008 x ( 99 + 1 ) 

      = 2008 x 100 

      = 200800 

b ) = ( 490 - 390 ) x 365 

      =      100 x 365 

     =   36500

c) = 2364 x ( 37 + 63 ) 

    = 2364 x 100

     = 236400

d ) = 12345 x ( 17 + 23 + 1 + 35 + 24 ) 

   = 12345 x  100

  = 1234500

\(\dfrac{21}{11}\times\dfrac{22}{17}\times\dfrac{68}{63}\) = \(\dfrac{42}{17}\times\dfrac{68}{63}\) = \(\dfrac{8}{3}\)

 Vì \(\dfrac{21}{11}\times\dfrac{22}{17}=\dfrac{21\times22}{11\times17}=\dfrac{42}{17}\)

 Vậy:

 \(\dfrac{21}{11}\times\dfrac{22}{17}\times\dfrac{63}{68}\) =\(\dfrac{42}{17}\times\dfrac{68}{63}\) =\(\dfrac{21\times2\times17\times4}{17\times21\times3}\) =\(\dfrac{8}{3}\) = 

d) Ta có: \(32\%-0.25:x=-\dfrac{17}{5}\)

\(\Leftrightarrow0.25:x=\dfrac{8}{25}+\dfrac{17}{5}=\dfrac{93}{25}\)

hay \(x=\dfrac{25}{372}\)

Vậy: \(x=\dfrac{25}{372}\)

e) Ta có: \(\left(x+\dfrac{1}{5}\right)^2+\dfrac{17}{25}=\dfrac{26}{25}\)

\(\Leftrightarrow\left(x+\dfrac{1}{5}\right)^2=\dfrac{9}{25}\)

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

Vậy: \(x\in\left\{\dfrac{2}{5};-\dfrac{4}{5}\right\}\)

f) Ta có: \(-\dfrac{32}{27}-\left(3x-\dfrac{7}{9}\right)^3=-\dfrac{24}{27}\)

\(\Leftrightarrow\left(3x-\dfrac{7}{9}\right)^3=\dfrac{-8}{27}\)

\(\Leftrightarrow3x-\dfrac{7}{9}=-\dfrac{2}{3}\)

\(\Leftrightarrow3x=\dfrac{1}{9}\)

hay \(x=\dfrac{1}{27}\)

g) Ta có: \(60\%\cdot x+0.4x+x:3=2\)

\(\Leftrightarrow\dfrac{4}{3}x=2\)

hay \(x=\dfrac{3}{2}\)

Vậy: \(x=\dfrac{3}{2}\)

h) PT \(\Leftrightarrow\left|\dfrac{20}{9}-x\right|=\dfrac{2}{9}\) \(\Rightarrow\left[{}\begin{matrix}\dfrac{20}{9}-x=\dfrac{2}{9}\\x-\dfrac{20}{9}=\dfrac{2}{9}\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}x=2\\x=\dfrac{22}{9}\end{matrix}\right.\)

  Vậy ...

i) PT \(\Leftrightarrow\dfrac{8}{5}+\dfrac{2}{5}x=\dfrac{16}{5}\) \(\Leftrightarrow\dfrac{2}{5}x=\dfrac{8}{5}\) \(\Leftrightarrow x=4\)

  Vậy ...

a) (37 - 17) . (-5) + 23 . (-13 - 17)

= 20 . (-5) + 23 . (-30)

= (-100) + (-690)

= -790

b) 63 . ( - 25 ) + 25 . (-23)

= (-63) . 25 + 25 . (-23)

= 25[(-63) + (-23)]

= 25 . (-86)

= -2150