a) `123 - 27 + 27 + 13 - 123`

`= (123 - 123) + (27 - 27) + 13`

`= 0 + 0 + 13`

`= 13`

`---`

b) `175 + 25 + 13 + 15 - 175 - 25`

`= (175-175)+(25-25)+25+13`

`=0+0+25+13`

`=28`

`---`

c) \(53\times39+47\times39+53\times21+47\times21\)

\(=\text{[}\left(53+47\right)\times39]+\left[\left(53+47\right)\times21\right]\)

\(=\left(100\times39\right)+\left(100\times21\right)\)

\(=3900+2100\)

`=6000`

`---`

d) \(49\times35+49\times16-49\times61\)

`=` \(49\times\left(35+16-61\right)\)

`=` \(49\times\left(-10\right)\)

`=-490`

Bài 1: Tính

a) Ta có: \(\left(-25\right)\cdot68+\left(-34\right)\cdot\left(-250\right)\)

\(=-25\cdot68+\left(-340\right)\cdot\left(-25\right)\)

\(=-25\cdot\left(68-340\right)\)

\(=-25\cdot\left(-272\right)\)

\(=6800\)

b) Ta có: \(1999+\left(-2000\right)+2001+\left(-2002\right)\)

\(=1999-2000+2001-2002\)

\(=-1-1=-2\)

c) Ta có: \(515+\left[72+\left(-515\right)+\left(-32\right)\right]\)

\(=515+72-515-32\)

\(=40\)

d) Ta có: \(\left(2736-75\right)-2736+175\)

\(=2736-75-2736+175\)

\(=100\)

e) Ta có: \(-2020-\left(157-2020\right)-\left(-257\right)\)

\(=-2020-157+2020+257\)

\(=100\)

Bài 2: Tìm x

a) Ta có: \(x-\left|-2\right|=\left|-18\right|\)

\(\Leftrightarrow x-2=18\)

hay x=20

Vậy: x=20

b) Ta có: \(2x-\left|+14\right|=\left|-14\right|\)

\(\Leftrightarrow2x-14=14\)

\(\Leftrightarrow2x=28\)

hay x=14

Vậy: x=14

c) Ta có: \(\left|x+4\right|+5=20-\left(-12-7\right)\)

\(\Leftrightarrow\left|x+4\right|+5=20+12+7\)

\(\Leftrightarrow\left|x+4\right|=39-5=34\)

\(\Leftrightarrow\left[{}\begin{matrix}x+4=34\\x+4=-34\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=30\\x=-38\end{matrix}\right.\)

Vậy: x∈{30;-38}

d) Ta có: \(15-\left|2-x\right|=\left(-2\right)^2\)

\(\Leftrightarrow15-\left|2-x\right|=4\)

\(\Leftrightarrow\left|2-x\right|=11\)

\(\Leftrightarrow\left[{}\begin{matrix}2-x=11\\2-x=-11\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-9\\x=13\end{matrix}\right.\)

Vậy: x∈{-9;13}

e) Ta có: \(\left|15-x\right|+\left|-25\right|=\left|-55\right|\)

\(\Leftrightarrow\left|15-x\right|+25=55\)

\(\Leftrightarrow\left|15-x\right|=30\)

\(\Leftrightarrow\left[{}\begin{matrix}15-x=30\\15-x=-30\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-15\\x=45\end{matrix}\right.\)

Vậy: x∈{-15;45}

g) Ta có: \(\left|17-\left(-4\right)\right|+\left|-24-\left(-5\right)\right|=\left|-x+3\right|\)

\(\Leftrightarrow\left|17+4\right|+\left|-24+5\right|=\left|3-x\right|\)

\(\Leftrightarrow\left|3-x\right|=40\)

\(\Leftrightarrow\left[{}\begin{matrix}3-x=40\\3-x=-40\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-37\\x=43\end{matrix}\right.\)

Vậy: x∈{-37;43}

A = 4 . 2 . 25 . 5 . 175 

A = 2² . 2 . 5² . 5 . 5² . 7 

A = 2²⁺¹ . 5²⁺¹⁺² . 7  

A = 2³ . 5⁵ .7

A = 175000

\(B=4^2-10^4:\left(50\cdot273-50\cdot73\right)\)

\(B=4^2-10^4:\left[50\cdot\left(273-73\right)\right]\)

\(B=4^2-10^4:\left(50\cdot200\right)\)

\(B=4^2-10^4:10^4=4^2-1=15\)

\(C=3\times53\times6+2\times9\times87-18\times40\)

\(C=18\times53+18\times87-18\times40\)

\(C=18\times\left(53+87-40\right)\)

\(C=18\times100=1800\)

Bạn dùng tính chất phân phối, giao hoán để làm nhé

A+0   B=2400   c=420

1) a) 53 x 39 + 47 x 39 - 53 x 21 - 47 x 21

= 39 x (53 + 47) - 21 x (53 - 47)

= 39 x 100 - 21 x 6

= 3900 - 126

= 3774

b) 2 x 53 x 12 + 4 x 6 x 87 - 3 x 8 x 40

= 1272 + 2088 - 960

= 3360 - 960

= 2400

c) 5 x 7 x 77 - 7 x 60 + 47 x 25 - 15 x 42

= 2695 - 420 + 1175 - 630

= 2275 + 545

= 2820

2) a) x : [(1800 + 600) : 30] = 560 : (315 - 35)

                     x : (2400 : 30) = 560 : 280

                                  x : 80 = 2

                                         x = 2 x 80

                                    => x = 160

b) [(250 - 25) : 15] : x = (450 - 60) : 130

                225 : 15 : x = 390 : 130

                         15 : x = 3

                               x  = 15 : 3

                           => x = 5

Học tốt!!!

Cau a các bạn đã làm mình làm câu b , c nhé

420  + 65 x 24 = (x+175) : 5 +30

1980 = (x+175) : 5 + 30

(x+175):5 = 1950

x+175 = 390

x = 215

7 x X - 24 = 5x X

=> 7 x X - 5 x X = 24

2x = 24

=> x = 12               

1: Tính

a: 27+ 55+ (-17) + (-55)

= (27-17) + (55-55)

= 10 + 0

= 10

b: (-92)+ (-251)+ (-8)+ 25

= -(92+8) - (251 - 25)

= -100 - 226

= -326

c: (235- 47) + (175- 53)

= 235 - 47 + 175 - 53

= (235+175) - (47+53)

= 410 - 100

= 310

d: (756- 217)- (183- 44)

= 756 - 217 - 183 + 44

= (756+44) - (217+183)

= 800 - 400

= 400

2: Tìm x, biết

\(\text{x. (x+ 3)= 0}\)

\(\Rightarrow\orbr{\begin{cases}x=0\\x+3=0\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=0\\x=-3\end{cases}}\)

vậy______

\(\text{(x-2). (5- x) = 0}\)

\(\Rightarrow\orbr{\begin{cases}x-2=0\\5-x=0\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=2\\x=5\end{cases}}\)

vậy________

(x- 3). (2x +1) = 7

=> x-3 và 2x + 1 thuộc Ư(7)

ta có bảng sau :

vậy x thuộc {4;3;2;-3;10;0;-4;-1}

a: 27+ 55+ (-17) + (-55)

=27 + 55 -17 - 55

=10

b: (-92)+ (-251)+ (-8)+ 25

= -92 - 251 - 8 + 25

=-326

c: (235- 47) + (175- 53)

=188 + 122

=310

d: (756- 217)- (183- 44)

=539 - 139

=400

Bài 1:

a) 27 + 55 + (-17) + (-55)

= (27 - 17) + (55 - 55)

= 10 + 0

= 10

b) (-92) + (-251) + (-8) + 25

= (-92 - 8) - (251 - 25)

= (-100) - 226

= -326

c) (235 - 47) + (175 - 53)

= 235 - 47 + 175 - 53

= (235 + 175) - (47 + 53)

= 410 - 100

= 310

d) (756 - 217) - (183 - 44)

= 756 - 217 - 183 + 44

= (756 + 44) - (217 + 183)

= 800 - 400

= 400

Bài này tự làm