38.x-x.12-x.16=40

<=> x(38-12-16)=40

<=> x.10=40

<=>x =4

\(Ta có: 38.x-x.12-x.16=40 \)

     \(\Rightarrow (38-12-16).x=40\)

     \(\Rightarrow 10.x=40\)

     \(\Rightarrow x=40:10\)

     \(\Rightarrow x=4\)

HOK TỐT...

thế mk lm đúng r

a) 2x - ( 40 - 52 ) = x + 12

       2x - 40 + 52 = x + 12

                        x = 0

b) 40 - x =-12 + 3x

         4x = 52

           x = 13

a) 2x - ( 40 - 52 ) = x + 12

       2x - 40 + 52 = x + 12

                        x = 0

b) 40 - x =-12 + 3x

         4x = 52

           x = 13

3,2 + 4,65 : 1,5 

=3,2+3,1

=6,3

347 + 418 + 123 + 12

=(347+123)+(418+12)

=470+430

=900

34 x 35 + 35 x 38 + 65 x 40 + 65 x 32

=35*(34+38)+65*(32+40)

=35*72+65*72

=72*(35+65)

=72*100

=7200

19 x 16 x 4 + 76 x 34

=76*16+76*34

=76*(16+34)

=76*50

=3800

136 x 68 + 16 x2 x 136 

=136*68+32*136

=136*(68+32)

=136*100

=13600

125 x 25 + 125 x 74 + 125

=125*(25+74+1)

=125*100

=12500

Tính bằng cách thuận tiện hả

3,2 + 4,65 : 1,5 = 3,2 + 3,1 = 6,3

347 + 418 + 123 + 12 = (347 + 123) + (418 + 12) = 470 + 430 = 900

34 x 35 + 35 x 38 + 65 x 40 + 65 x 32 = 35 x ( 34 + 38) + 65 x (40 + 32) = 35 x 72 + 65 x 72 = 72 x (35 + 65) = 72 x 100 = 7200

19 x 16 x 4 + 76 x 34

136 x 68 + 16 x2 x 136 

125 x 25 + 125 x 74 + 125

a) x = 190            

b) x = 344           

c) x = 4                

d) x = 20

a) Ta có : \(x⋮12\Rightarrow x\in B\left(12\right)=\left\{12;24;36;48;...\right\}\) (sửa \(x\in12\rightarrow x⋮12\))

mà \(0< x< 40\)

\(\Rightarrow x\in\left\{12;24;36\right\}\)

b) \(16⋮x\Rightarrow x\in U\left(16\right)=\left\{1;2;4;8;16\right\}\left(x\inℕ\right)\) (sửa \(16\in x\rightarrow16⋮x\))

\(\frac{12}{16}=-\frac{x}{4}=\frac{21}{y}=\frac{z}{-80}\)

Ta có : \(\frac{12}{16}=-\frac{x}{4}\Rightarrow16.-x=12.4\Rightarrow16.-x=48\)

\(\Rightarrow-x=3\Rightarrow x=-3\)

\(\frac{12}{16}=\frac{21}{y}\Rightarrow12.y=16.21\Rightarrow12.y=336\)

\(\Rightarrow y=28\)

\(\frac{12}{16}=\frac{z}{-80}\Rightarrow16.z=12.-80\Rightarrow16.z=-960\)

\(\Rightarrow z=60\)

Vậy x = - 3 ; y = 28 ; z = 60

Ta có:

\(\frac{12}{16}=\frac{-x}{4}=\frac{21}{y}=\frac{z}{-80}\)

\(\Leftrightarrow\frac{12}{16}=\frac{-x}{4}=\frac{21}{y}=\frac{-z}{80}\) (Chuyển mẫu âm thành dương)

\(\frac{-x}{4}=\frac{12}{16}=\frac{12:\left(-4\right)}{16:\left(-6\right)}=\frac{-3}{-4}=\frac{3}{4}\Rightarrow x=-3\) (Ta chuyển mẫu âm thành dương)

\(\frac{21}{y}=\frac{3}{4}=\frac{3.7}{4.7}=\frac{21}{28}\Rightarrow y=28\)

\(\frac{-z}{80}=\frac{21}{28}\) ( Vì 80 : 28 không hết) \(\Rightarrow z=\varnothing\)

 \(\Rightarrow\hept{\begin{cases}-3\\28\\\varnothing\end{cases}}\)

Vì \(\frac{12}{16}=\frac{-x}{4}\)nên 12 . 4 = 16 . (-x) = 48.

Suy ra :\(-x=\frac{48}{16}=3\)hay x = -3

Vì\(\frac{21}{y}=\frac{12}{16}\)nên y . 12 = 21. 16 =336

Suy ra :\(y=\frac{336}{12}=28\)

Vì \(\frac{z}{80}=\frac{12}{16}\)nên z . 16 = 12 . 80 = 960

Suy ra :\(z=\frac{960}{16}=60\)

Vậy x = -3 ; y = 28 ; z = 60

+) 187 x ( 38 + 62 ) - 87 x ( 62 + 38 )

= ( 62 + 38 ) x ( 187 - 87 )

= 100 x 100

= 10000

p/s : làm từng phần đợi mk chút ^^

25 x { 32 : [ 12 - 4 + 4 x ( 16 : 8 ) ] }

= 25 x { 32 : [ 8 + 4 x 2 ] }

= 25 x { 32 : 16 }

= 25 x 2

= 50

\(187\times\left(38+62\right)-87\times\left(62+28\right).\)

\(=187\times100+87\times100\)

\(=100\times\left(187-87\right)\)

\(=100\times100\)

\(=10000\)

\(25\times\left\{32:\left[12-4+4\times\left(16:8\right)\right]\right\}\)

\(=25\left\{32:\left[12-4+4\times2\right]\right\}\)

\(=25\times\left\{32:\left[12-4+8\right]\right\}\)

\(=25\times\left\{32:16\right\}\)

\(=25\times2=50\)

`12^4 .x-3.x=145-225:51`

`=>20736x-3x=145-75/17`

`=>20733x=2390/17`

`=>x=2390/17:20733`

`=>x=2390/352461`

2⁴x-3x=145-225:51(sửa đề)

=> 13x=145-75/17

=> 13x=2390/17

=> x=2390/221

Ta có: \(\hept{\begin{cases}|x-40|\ge0;\forall x,y\\|x-y+10|\ge0;\forall x,y\end{cases}}\)

\(\Rightarrow|x-40|+|x-y+10|\ge0;\forall x,y\)

Do đó: \(|x-40|+|x-y+10|=0\)

\(\Leftrightarrow\hept{\begin{cases}|x-40|=0\\|x-y+10|=0\end{cases}}\Leftrightarrow\hept{\begin{cases}x=40\\y=50\end{cases}}\)