Bài 2: 

a: =>x=0 hoặc x=-3

b: =>x-2=0 hoặc 5-x=0

=>x=2 hoặc x=5

c: =>x-1=0

hay x=1

Bài 2:

a: (x+3)-7=10

=>x+3-7=10

=>x-4=10

=>x=10+4

=>x=14

b: \(2\left(5-x\right)=2^2-2^3\)

=>2(5-x)=4-8=-4

=>5-x=-2

=>x=5+2=7

c: 2x+1 là bội của x-3

=>2x+1⋮x-3

=>2x-6+7⋮x-3

=>7⋮x-3

=>x-3∈{1;-1;7;-7}

=>x∈{4;2;10;-4}

Bài 1:

a: 34-245-234-55

=(34-234)-(245+55)

=-200-300

=-500

b: \(113\cdot39-39-12\cdot39\)

\(=39\left(113-1-12\right)\)

\(=39\cdot100=3900\)

c: \(-200-100:\left\lbrack13-2\left(17-4\cdot5\right)^2\right\rbrack\cdot1^{2021}\)

\(=-200-100:\left\lbrack13-2\left(17-20\right)^2\right\rbrack\)

\(=-200-100:\left\lbrack13-2\cdot3^2\right\rbrack=-200-100:\left(13-18\right)\)

=-200-100:(-5)

=-200+20

=-180

\(a,\Leftrightarrow25x^2-70x+49-25x^2=32\\ \Leftrightarrow-70x=-17\Leftrightarrow x=\dfrac{17}{70}\\ b,\Leftrightarrow x^2-6x+9+x^2+2x+1-5=0\\ \Leftrightarrow2x^2-4x+5=0\\ \Leftrightarrow2\left(x^2-2x+1\right)+3=0\\ \Leftrightarrow2\left(x-1\right)^2=-3\Leftrightarrow\left(x-1\right)^2=-\dfrac{3}{2}\left(\text{vô lí}\right)\\ \Leftrightarrow x\in\varnothing\)

\(a,x+75=21\\ \Rightarrow x=21-75\\ \Rightarrow x=-54\)

\(b,\left(-30\right)-x=-45\\ \Rightarrow x=\left(-30\right)-\left(-45\right)\\ \Rightarrow x=15\)

a: x=-54

b: x=15

1,

a, \(x\)x 124= 4829-365

 \(x\)x 124 = 4464

\(x\)= 4464 :124

\(x\)= 36.

b,\(x\)x 137 = 25 x 3 

   \(x\)x 137 = 75

\(x\)= \(\frac{75}{137}\)

2,

\(\frac{4}{5}\)x\(\frac{3}{7}+\frac{4}{5}\)x\(\frac{6}{7}-\frac{4}{5}\)x\(\frac{4}{10}\)

=\(\frac{4}{5}\)x\(\left(\frac{3}{7}+\frac{6}{7}-\frac{4}{10}\right)\)=\(\frac{4}{5}\)x\(\frac{31}{35}\)\(\frac{124}{175}\)

\(\text{Bài }1\text{ : Tìm }x\text{ : }\)

\(a,\text{ }x\text{ x }124=4829-365\)

     \(x\text{ x }124=4464\)

     \(x=4464\text{ : }124\)

     \(x=36\)

\(b,\text{ }x\text{ x }137=25\text{ x }3\)

     \(x\text{ x }137=75\)

     \(x=75\text{ : }137\)

     \(x=\frac{75}{137}\)

\(\text{Bài }2\text{ : Tính bằng cách thuận tiện nhất : }\)

      \(\frac{4}{5}\text{ x }\frac{3}{7}+\frac{4}{5}\text{ x }\frac{6}{7}-\frac{4}{5}\text{ x }\frac{4}{10}\)

\(=\frac{4}{5}\text{ x }\left(\frac{3}{7}+\frac{6}{7}-\frac{4}{10}\right)\)

\(=\frac{4}{5}\text{ x }\left(\frac{9}{7}-\frac{4}{10}\right)\)

\(=\frac{4}{5}\text{ x }\frac{31}{35}\)

\(=\frac{124}{175}\)

a: x=36-72=-36

d: =>x-5=0

hay x=5

a) x + 72 = 36

    x         = 36 - 72 = -36

b) 16 x² = 64

         x² = 64 : 16 = 4

         x² = 2²   

    →  x    = 2

c) (5 . x - 2) - 64 = -36

    (5 . x - 2)        = -36 + 64

     5 . x - 2         =      28

     5 . x              = 28 + 2 = 30

          x              = 30 : 5 = 6

d) (2x - 10) . (5 - x) = 0

     x = 5

A,-8

B,-36

C,-80

{Mình tính bằng máy tính }

bạn thực hiện phép tính giúp mình với

a: \(245\times11+11\times365\)

=11x(245+365)

=11x610

=6710

b: \(78\times75+75\times89+75\times123\)

\(=75\times\left(78+89+123\right)\)

=75x290

=21750

c: \(2\times250\times50\times8\)

=2x50x250x8

=100x2000

=200000

d: (76:7)x4

=76x4:7

=304/7

e: (372x15)x9

=5580x9

=50220

f: (56x23x4):7

=56:7x23x4

=8x92

=736

a) Ta có: \(\left|-5\right|+\left|x-1\right|=\left|7\right|\)

\(\Leftrightarrow\left|x-1\right|+5=7\)

\(\Leftrightarrow\left|x-1\right|=2\)

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

Vậy: \(x\in\left\{3;-1\right\}\)

b) Ta có: \(2\cdot\left|2x-4\right|-\left|-4\right|=\left|-50\right|\)

\(\Leftrightarrow4\cdot\left|x-2\right|-4=50\)

\(\Leftrightarrow4\cdot\left|x-2\right|=54\)

\(\Leftrightarrow\left|x-2\right|=\dfrac{27}{2}\)

\(\Leftrightarrow\left[{}\begin{matrix}x-2=\dfrac{27}{2}\\x-2=-\dfrac{27}{2}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{31}{2}\left(loại\right)\\x=-\dfrac{23}{2}\left(loại\right)\end{matrix}\right.\)

Vậy: \(x\in\varnothing\)

a, | -5 | + | x-1 | = | 7 |

         5 + | x - 1 | = 7 

               | x - 1 | = 2

TH1  x -1 = 2

        x = 3

TH2 x -1 = -2

        x= -1