B1:

\(a.301^2=\left(300+1\right)^2=300^2+2.300.1+1^2\\ =90000+600+1=90601\\ b.88^2+2.88.12+12^2=\left(88+12\right)^2=100^2=10000\\ c.99.100=100^2-100=10000-100=9900\\ d,153^2+94.153+47^2=153^2+2.153.47+47^2=\left(153+47\right)^2=200^2=40000\)

B2:

\(A=x^2-20x+101\\ =x^2-2.x.10+10^2+1\\ =\left(x-10\right)^2+1\ge1\forall x\in R\left(Vì:\left(x-10\right)^2\ge0\forall x\in R\right)\\ \Rightarrow min_A=1\Leftrightarrow x-10=0\Leftrightarrow x=10\)

`@` `\text {Ans}`

`\downarrow`

`1,`

`a)`

`5 \times 72 \times 10 \times 2`

`= 5 \times 2 \times 10 \times 72`

`= 10 \times 10 \times 72`

`= 100 \times 72`

`= 7200`

`b)`

`40 \times 125`

`= 4 \times 10 \times 25 \times 5`

`= (5 \times 10) \times (4 \times 25)`

`= 50 \times 100`

`= 5000`

`c)`

`4 \times 2021 \times 25`

`= (4 \times 25) \times 2021`

`= 100 \times 2021`

`= 202100`

`d)`

`16 \times 6 \times 25`

`= 4 \times 4 \times 6 \times 25`

`= (4 \times 25) \times 4 \times 6`

`= 100 \times 24`

`= 2400`

`2,`

`a)`

`24 \times 57 + 43 \times 24`

`= 24 \times (57+43)`

`= 24 \times 100`

`= 2400`

`b)`

`12 \times 19 + 80 \times 12 +12`

`= 12 \times (19 + 80 + 1)`

`= 12 \times 100`

`= 1200`

`c)`

`(36 \times 15 \times 169) \div (5 \times 18 \times 13)`

`= 36 \times 15 \times 169 \div 5 \div 18 \div 13`

`= 6 \times 6 \times 3 \times 5 \times 13 \times 13 \div 5 \div 3 \times 6 \div 13`

`= (6 \div 6) \times (3 \div 3) \times (5 \div 5) \times (13 \div 13) \times 6 \times 13`

`= 6 \times 13`

`= 78`

`d)`

`(44 \times 52 \times 60) \div ( 11 \times 13 \times 15)`

`= 44 \times 52 \times 60 \div 11 \div 13 \div 15`

`= 4 \times 11 \times 13 \times 4 \times 15 \times 4 \div 11 \div 13 \div 15`

`= (11 \div 11) \times (13 \div 13) \times (15 \div 15) \times 4 \times 4 \times`

`= 4 \times 4 \times 4`

`= 64`

`3,`

`a)`

`x - 280 \div 35 = 5 \times 54`

`x - 8 = 270`

`x = 270 + 8`

`x = 278`

`b)`

`(x - 280) \div 35 = 54 \div 4`

`(x - 280) \div 35 = 13,5`

`x - 280 = 13,5 \times 35`

`x - 280 = 472,5`

`x = 472,5 + 280`

`x = 752,5`

`c)`

`(x - 128 + 20) \div 192 = 0`

`x - 128 + 20 = 0 \times 192`

`x - 128 + 20 = 0`

`x - 108 = 0`

`x = 0 + 108`

`x = 108`

`d)`

`4 \times (x + 200) = 460 + 85 \times 4`

`4 \times (x+200) = 460 + 340`

`4 \times (x+200) = 800`

`x + 200 = 800 \div 4`

`x + 200 = 200`

`x = 200 - 200`

`x = 0`

`4,`

`a)`

`7/12 - 5/12`

`= (7 - 5)/12`

`= 2/12`

`= 1/6`

`b)`

`8/11 + 19/11`

`= (8+19)/11`

`= 27/11`

`c)`

`3/8 + 5/12`

`= 9/24 + 10/24`

`= 19/24`

`d)`

`3/4 + 7/12`

`= 9/12 + 7/12`

`= 16/12`

`= 4/3`

`5,`

`a)`

`x - 6/7 = 5/2`

`x = 5/2 + 6/7`

`x = 47/14`

`b)`

`12/7 \div x + 2/3 = 7/5`

`12/7 \div x = 7/5 - 2/3`

`12/7 \div x = 11/15`

`x = 12/7 \div 11/15`

`x = 180/77`

`@` `\text {Kaizuu lv uuu}`

Bài 2: 

a: =>x-35=-23

=>x=12

b: =>|x-8|=13

=>x-8=13 hoặc x-8=-13

=>x=21 hoặc x=-5

Bài 1: 

a: =42-98-42+12-12=-98

b: =10x4x3x(-25)=40x(-25)x3=-1000x3=-3000

a) Tính bằng cách thuận tiện nhất:

134 x 4 x 5

= 134 x (4 x 5)

= 134 x 20 = 1680

5 x 36 x 2

= 36x (5 x 2)

= 36 x 10 = 360

42 x 2 x 7 x5

= (42 x 7) x (2 x5)

= 294 x 10 = 2940

b) 137 x 3 + 137 x 97

= 137 x (3 + 97)

= 137 x 100 = 13700

94 x 12 + 94 x 88

= 94 x (12 + 88)

= 94 x 100 = 9400

428 x 12 - 428 x 2

= 428 x (12 - 2) = 4280

537 x 39 - 537 x 19

= 537 x (39 - 19)

= 537 x 20 = 10740

a) |x + 4| = 17

=> \(\orbr{\begin{cases}x+4=17\\x+4=-17\end{cases}}\)

=> \(\orbr{\begin{cases}x=13\\x=-21\end{cases}}\)

b) (7 - x) - (25 + 7) = -25

=> (7 - x) - 32 = -25

=> 7 - x = -25 + 32

=> 7 - x = 7

=> x = 7 - 7

=> x = 0

c. |x + 5| = |-7|

=> |x + 5 | = 7

=> \(\orbr{\begin{cases}x+5=7\\x+5=-7\end{cases}}\)

=> \(\orbr{\begin{cases}x=2\\x=-12\end{cases}}\)

2) 4 . (-5)² + 2 . (-15)

= 2. 2 . 25 + 2 . (-15)

= 2.(2 . 25 - 15)

= 2 . 35

= 70

1/ 

a) | x+4 | = 17

\(\Rightarrow\)x+4 = 17 hoặc x+4 = -17

        x      = 13         x      = -21

b) ( 7 - x ) - ( 25 + 7 ) = -25

     7 - x                      = -25 + 25 + 7

     7 - x                      = 7

          x                      = 0

c) | x + 5 | = 7

\(\Rightarrow\)x + 5 = 7 hoặc x + 5 = -7

         x        = 2         x        = -12

2/

    4 . ( -5 )² + 2 . ( -15 )

= 4 . 25 + 2 . ( -15 )

= 100 + ( -30 )

= 70

Hk tốt

a) 320 x 63 - 16 x 20 + 32 x 370

= 320 x 63 - 320 x + 320 x 37

= 320 x ( 63 - 1 + 37 )

= 320 x 99 

= 320 x ( 100 - 1 )

= 320 x 100 - 320

= 32000 - 320 = 31 680

b) 35 x 61 + 215 x 5 + 35 x 39 + 57 x 25

= 5 x 427 + 5 x 215 + 5 x 273 + 5 x 285

= 5 x ( 427 + 215 + 273 + 285 ) 

= 5 x 1200 = 6000

c) 34 x 24 - 94 x 6 + 83 x 48 - 47 x 88

= 204 x 4 - 4 x 141 + 996 x 4 - 1034 x 4

= 4 x ( 204 - 141 + 996 - 1034 )

= 4 x 25 = 100

428 x 12 - 428 x 2

= 428 x (12 - 2) = 4280

a) \(\frac{25}{9}-\frac{12}{13}x=\frac{7}{9}\)

=> \(\frac{12}{13}x=\frac{25}{9}-\frac{7}{9}=\frac{18}{9}=2\)

=> \(x=2:\frac{12}{13}=2\cdot\frac{13}{12}=\frac{13}{6}\)

b) \(x:\frac{13}{3}=-2,5\)

=> \(x:\frac{13}{3}=-\frac{5}{2}\)

=> \(x=\left(-\frac{5}{2}\right)\cdot\frac{13}{3}=-\frac{65}{6}\)

c) \(\frac{x}{3}-\frac{1}{4}=-\frac{5}{6}\)

=> \(\frac{4x-3}{12}=-\frac{10}{12}\)

=> 4x - 3 = -10

=> 4x = -10 + 3 = -7

=> x = -7/4

Bài 2 :

\(A=a\cdot\frac{1}{3}+a\cdot\frac{1}{4}-a\cdot\frac{1}{6}=a\left(\frac{1}{3}+\frac{1}{4}-\frac{1}{6}\right)=a\cdot\frac{5}{12}\)

Thay a = -3/5 vào biểu thức ta có : \(A=\left(-\frac{3}{5}\right)\cdot\frac{5}{12}=\frac{-3}{12}=\frac{-1}{4}\)

\(B=b\cdot\frac{5}{6}+b\cdot\frac{3}{4}-b\cdot\frac{1}{2}=b\left(\frac{5}{6}+\frac{3}{4}-\frac{1}{2}\right)=b\cdot\frac{13}{12}\)

Thay b = 12/13 vào ta được kết quả là 1

a ) \(\frac{25}{9}-\frac{12}{13}\cdot x=\frac{7}{9}\)

\(\Rightarrow\frac{12}{13}\cdot x=\frac{25}{9}-\frac{7}{9}=\frac{18}{9}=2\)

\(\Rightarrow x=2\div\frac{12}{13}=2\cdot\frac{13}{12}=\frac{13}{6}\)

Vậy ...

b ) \(x\div\frac{13}{3}=-\frac{5}{2}\)

\(\Rightarrow x\div\frac{13}{3}=-\frac{5}{2}\)

\(\Rightarrow x=\left(-\frac{5}{2}\right)\cdot\frac{13}{3}=-\frac{65}{6}\)

Vậy ..

c ) \(\frac{x}{3}-\frac{1}{4}=-\frac{5}{6}\)

\(\Rightarrow\frac{4x-3}{12}=-\frac{10}{12}\)

\(\Rightarrow4x-3=-10\)

\(\Rightarrow4x=-10+3=-7\)

\(\Rightarrow x=-\frac{7}{4}\)

Vậy ....

Bài 2 : 

\(A=a\cdot\frac{1}{3}+a\cdot\frac{1}{4}-a\cdot\frac{1}{6}=a\left(\frac{1}{3}+\frac{1}{4}-\frac{1}{6}=a\cdot\frac{5}{12}\right)\)

Thay \(a=-\frac{3}{5}\)vào biểu thức ta được : \(A=\left(-\frac{3}{5}\right)\cdot\frac{5}{12}=-\frac{3}{12}=-\frac{1}{4}\)

\(B=b\cdot\frac{5}{6}+b\cdot\frac{3}{4}-b\cdot\frac{1}{2}=b\left(\frac{5}{6}+\frac{3}{4}-\frac{1}{2}\right)=b\cdot\frac{13}{12}\)

Thay \(b=\frac{12}{13}\)vào biểu thức , dễ thấy kết quả bằng 1 .