- x - 2/3 = - 6/7

=> - x = - 6/7 + 2/3

=> - x = - 4/21

=> x = 4/21

Vậy x = 4/21 

-x - 2/3 = - 6/7

- x = - 6/7 + 2/3

- x =  - 4/21

x = 4/21

Vậy x=4/21

#Emma Nguyen

a) 3,(4) =  3 + 4/9 = 3.9 + 4/9 = 31/9

b) 1,4(51) = 1 + 0,4 + 51/99 = 1.99 + 0,4.99 + 51/99 =  316/165

c) - 2,(412) = - 2 + 412/999 = (-2).999 + 412/999 = -1586/999

d) 3,1(45) = 3 + 0,1 + 45/99 = 3.99 + 0,1.99 + 45/99 = 391/110 

a) \(A=\frac{3x-1}{x-1}=\frac{3x-3+2}{x-1}=3+\frac{2}{x-1}\inℤ\Leftrightarrow\frac{2}{x-1}\inℤ\)

mà \(x\inℤ\)nên \(x-1\inƯ\left(2\right)=\left\{-2,-1,1,2\right\}\)

\(\Leftrightarrow x\in\left\{-1,0,2,3\right\}\).

 \(B=\frac{2x^2+x-1}{x+2}=\frac{2x^2+4x-3x-6+5}{x+2}=2x-3+\frac{5}{x+2}\inℤ\Leftrightarrow\frac{5}{x+2}\inℤ\)

mà \(x\inℤ\)nên \(x+2\inƯ\left(5\right)=\left\{-5,-1,1,5\right\}\)

\(\Leftrightarrow x\in\left\{-7,-3,-1,3\right\}\)

b) Để \(A\)và \(B\)cùng nguyên thì \(x\in\left\{-1,3\right\}\).

a)\(\frac{5.27^3.4^5}{6^5}:\left(\frac{5^5.2^4}{10^4}.\frac{2^6.3^4}{6^4}\right)=\frac{5.\left(3^3\right)^3.\left(2^2\right)^5}{\left(2.3\right)^5}:\left(\frac{5^4.2^4.5}{10^4}.\frac{2^4.3^4.2^2}{6^4}\right)\)

\(=\frac{5.3^9.2^{10}}{2^5.3^5}:\left(\frac{10^4.5}{10^4}.\frac{6^4.4}{6^4}\right)=5.3^4.2^5:\left(5.4\right)=\frac{5.3^4.2^5}{5.2^2}=3^4.2^3=648\)

b) \(\frac{5-\frac{5}{3}-\frac{5}{9}-\frac{5}{27}}{8-\frac{8}{3}-\frac{8}{9}-\frac{8}{27}}=\frac{5\left(\frac{1}{3}-\frac{1}{9}-\frac{1}{27}\right)}{8\left(\frac{1}{3}-\frac{1}{9}-\frac{1}{27}\right)}=\frac{5}{8}\)

Phép tính còn lại bạn ghi rõ để mk làm tiếp

Sorry, thêm vào giữa 2 ps dấu : giúp mik nhé

8*(5/17)-(-8*2/-4):(4/3-4/12

=40/17-4:(4/3-1/3)

=40/17-4:1

=40/17-68/17

=-28/17

(mk lm hơi tắt mong bạn thông cảm

\(\left(1-\frac{4}{1}\right)\left(1-\frac{4}{9}\right)\left(1-\frac{4}{25}\right)...\left(1-\frac{4}{\left(2x+1\right)^2}\right)\) \(\left(ĐK:n\ge1\right)\)

\(=\left(\frac{1-4}{1}.\frac{9-4}{9}.\frac{25-4}{25}....\frac{\left(2n-1\right)^2-4}{\left(2n-1\right)^2}\right)\)

\(=\frac{\left(1-2\right)\left(1+2\right)}{1}.\frac{\left(3-2\right)\left(3+2\right)}{3.3}.\frac{\left(5-2\right)\left(5+2\right)}{5.5}....\frac{\left(2n-3\right)\left(2n+1\right)}{\left(2n-1\right)^2}\)

\(=\frac{\left(-1\right).3}{1}.\frac{1.5}{3.3}.\frac{3.7}{5.5}....\frac{\left(2n-3\right)\left(2n+1\right)}{\left(2n-1\right)\left(2n-1\right)}\)

\(=-\frac{2n+1}{2n-1}\)

Sửa giúp mình dòng đầu lại thành:

\(\left(1-\frac{1}{4}\right)\left(1-\frac{4}{9}\right)\left(1-\frac{4}{25}\right)...\left(1-\frac{4}{\left(2n-1\right)^2}\right)\)

Nguồn: Google

hinhd vẽ đâu bn