Bài 9: Số thập phân hữu hạn. Số thập phân vô hạn tuần hoàn

\(0,\left(1\right)=\dfrac{1}{9}\)

\(0,\left(3\right)=\dfrac{1}{3}\)

\(0,\left(7\right)=\dfrac{7}{9}\)

\(0,\left(12\right)=\dfrac{12}{99}\)

\(0,0\left(5\right)=\dfrac{1}{18}\)

\(1,\left(2\right)=\dfrac{11}{9}\)

\(1,\left(34\right)=\dfrac{133}{99}\)

\(5,0\left(6\right)=\dfrac{76}{15}\)

\(8,2\left(7\right)=\dfrac{149}{18}\)

\(0,00\left(81\right)=\dfrac{9}{1100}\)

a: 0,(47)+0,(52)

=47/99+52/99

=99/99=1

b: =1/3x3=1

B=(2,15-167/150):(16/25-1/5+7/25)-11,125

=311/300:18/25-11,125

=-523/54

<=> 1/3 - 3x = -1/27

<=> 3x = 1/3 - -1/27 = 10/27

<=> x = 10/27 : 3 = 10/81

\(TH1\\ \left(\dfrac{1}{5}-\dfrac{3}{2}x\right)^2=\left(\dfrac{3}{2}\right)^2\\ \dfrac{1}{5}-\dfrac{3}{2}x=\dfrac{3}{2}\\ \dfrac{3}{2}x=\dfrac{1}{5}-\dfrac{3}{2}\\ \dfrac{3}{2}x=-\dfrac{13}{10}\\ x=-\dfrac{13}{15}\\ TH2\\ \left(\dfrac{1}{5}-\dfrac{3}{2}x\right)^2=\left(-\dfrac{3}{2}\right)^2\\ \dfrac{1}{5}-\dfrac{3}{2}x=-\dfrac{3}{2}\\ \dfrac{3}{2}x=\dfrac{1}{5}-\left(-\dfrac{3}{2}\right)\\ \dfrac{3}{2}x=\dfrac{17}{10}\\ x=\dfrac{17}{15}\)

(2x - 1)³ = 8

<=> (2x - 1)³ = 2³

<=> 2x - 1 = 2

<=> 2x = 3

<=> x = 3/2

\(\left(2x-1\right)^3=2^3\\ 2x-1=2\\ 2x=2+1\\ 2x=3\\ x=\dfrac{3}{2}\)

kq 1,5

\(A=\left(-1+\dfrac{17}{5}+\dfrac{1}{4}\right).\left(-4\right)\\ A=\left(\dfrac{-20+17.4+5}{20}\right)\left(-4\right)\\ A=\dfrac{53}{20}.\left(-4\right)\\ A=-\dfrac{53}{5}\)

`a, 1, (6) = 5/3`

`b, 2, (3) = 7/3`

`c, -2,23(123) = -743/333`

`d, 1,1(234) = 1247/1110`

`e, 2,12(345) = 70711/33300`

`f, 0,(15) = 5/33`

f: 0,(15)=15/99=5/33

a: 1,1(234)=1247/1110

b: 1,(6)=5/3

c: 2,(3)=7/3

d: -2,23(123)=-743/333

Mình trả lời câu hỏi này của bạn 1 lần rồi thì phải nên không trả lời lại nữa nhé.
Bạn tham khảo cách chuyển: https://vietjack.com/toan-lop-7/cach-viet-so-thap-phan-vo-han-tuan-hoan-duoi-dang-phan-so-toi-gian-cuc-hay.js

a: 1,1(234)=1247/1110

b: 1,(6)=5/3

c: 2,(3)=7/3

d: -2,23(123)=-743/333

a) `1,1(234)=1247/1110`

b) `1,(6)=5/3`

c) `2,(3)=7/3`

d) `-2,23(123)=-743/333`

e) `2,12(345)=70711/33300`

a: u1=2^2-1

u2=3^2-1

...

u100=101^2-1=10200

c: u1=2

u2=5=2+3

u3=10=2+3+5

u4=2+3+5+7

...

u100=2+3+...+297=14852