Bài 1 : 

a) A= (1;2;3;4;5)

b) B= ( 63;64;65;66;67;68;69;70)

Bài 2 :

a) 10x-5 = 11.5-10

10x-5 = 55-10

10x=45+5

10x=50

x=5

b) 27-3x=9.2-3

27-3x = 18-3

27-3x=15

3x=27-15

3x=12

x=4

c) 4x-15=12:12

4x-15=1

4x=16

x=4

d) 2+13x=14.2

13x=28-2

13x=26

x=2

a) \(10x-5=45\)

\(10x=40\)

\(x=4\)

b) \(27-3x=15\)

\(3x=27-15=12\)

\(x=\dfrac{12}{3}=4\)

c) \(4x-15=1\)

\(4x=16\)

\(x=\dfrac{16}{4}=4\)

d) \(2+13x=28\)

\(13x=26\)

\(x=\dfrac{26}{13}=2\)

=23x(57+63-20)

=23 x 100

=2300

\(23.57+63.23-23.20\\ =23.\left(57+63-20\right)\\ =23.100\\ =2300\)

thôi đừng trách bản thân về bn nữa.Bạn làm được mà

`(x+2)*5 -23=12`

`=> (x+2)*5=12+23`

`=> (x+2)*5= 35`

`=>x+2=35:5`

`=>x+2=7`

`=>x=7-2`

`=>x=5`

\(A=8\cdot17\cdot125=\left(125\cdot8\right)\cdot17=1000\cdot17=17000\)

\(B=\left(25\cdot4\right)\cdot37=100\cdot37=3700\)

\(C=\left(75+50-25\right)\cdot58=100\cdot58=5800\)

\(D=\left(39+63-2\right)\cdot27=100\cdot27=2700\)

A=8.17.125= (8.125).17= 1000.17=17000

b=4.37.25=(4.25).37=100.37=3700

c= 58.75+58.50-58.25= 58.(75+50 - 25)= 58.100=5800

d=27.39+27.63-2.27= 27.(39+63-2)=27.100=2700

\(531+\left(28-x\right)=735\\ 28-x=735-531\\ 28-x=204\\ x=28-204\\ x=-176\)

@ Mai Trung Hải Phong : em cũng làm vậy, mà nó âm nên em sợ saii ak!!

\(4^x+4^{x+1}=320\\ \Leftrightarrow4^x.\left(1+4\right)=320\\ \Leftrightarrow4^x.5=320\\ \Leftrightarrow4^x=\dfrac{320}{5}=64=4^3\\ Vậy:x=3\\ ----\\ 3^{x+3}-3^x=234\\ \Leftrightarrow3^x\left(3^3-1\right)=234\\ \Leftrightarrow3^x.26=234\\ \Leftrightarrow3^x=\dfrac{234}{26}=9=3^2\\ vậy:x=2\)

\(M=\left\{n^2+1|n\inℕ\right\}\)

\(M=\left\{k\inℕ^∗|k=k^2+1,k\le401\right\}\)

a) \(23197=2\cdot10^4+3\cdot10^3+10^2+9\cdot10^1+7\)

b) \(203184=2\cdot10^5+3\cdot10^3+10^2+8\cdot10^1+4\)

Câu b chưa có vế phải

a) (x-3)(y+1)=5

xy-3y+x-3=5

xy-3y=2

y(x-3)=2

Lập bảng.