\(-\dfrac{49}{81}.\dfrac{27}{-77}\)
\(=\dfrac{49.27}{81.77}\)
\(=\dfrac{7.7.27}{3.27.7.11}\)
\(=\dfrac{7}{3.11}\)
\(=\dfrac{7}{33}\)

sai

                              12/49  >   13/47

                                64/85   >  73/81

                                19/31    > 17/35 

                                 67/77   >  73/83

\(\dfrac{1}{27}\cdot3^x=81\)

\(\Rightarrow3^x=81:\dfrac{1}{27}\)

\(\Rightarrow3^x=2187\)

\(\Rightarrow3^x=3^7\)

\(\Rightarrow x=7\)

Ta có :\(\frac{1}{27}=\frac{81^n}{3^n}\)

\(\frac{1}{27}=81^n:3^n=27^n\)

\(27^n=27^{-1}\)

n = -1

Vậy n = -1

1/27 x 81^n =3^n

=>(1/3)^3 x (3^4)^n =3^n

=>(3^ -1)^3 x 3^4n = 3^n

=>3^-3 x 3^4n=3^n

=>3^(-3+4n)=3^n

=> -3+4n=n

=> 4n-n=3

=> 3n =3=>n=1

e cần gấp ạ

a: Phân số tối giản là 25/27; 77/79

b: 51/34=3/2

77/99=7/9

120/201=40/67

351/621=13/23

\(\frac{16}{27}\) tích mình nha !

a) \(\frac{75^3.3^7}{81^4.5^6}=\frac{5^3.3^3.5^3.3^7}{\left(3^4\right)^4.5^6}=\frac{5^6.3^3.3^7}{3^{16}.5^6}=\frac{3^{10}}{3^{16}}=\frac{1}{3^6}=\frac{1}{729}\)
b) \(\frac{6^6.4^2}{3^{12}.2^8}=\frac{2^6.3^6.\left(2^2\right)^2}{3^{12}.2^8}=\frac{2^6.3^6.2^4}{3^{12}.2^8}=\frac{2^{10}.3^6}{3^{12}.2^8}=\frac{2^2.1}{3^6}=\frac{4}{729}\)
c) \(\frac{34^5.2^5}{2^{14}.17^5}=\frac{2^5.17^5.2^5}{2^{14}.17^5}=\frac{2^{10}}{2^{14}}=\frac{1}{2^4}=\frac{1}{16}\)

 1/2 x 2 mũ n cộng 4 x 2 mũ n = 9 x 2 mũ n