a) 80<243 nên \(\frac{1}{80}>\frac{1}{243}\)

\(\Rightarrow\left(\frac{1}{80}\right)^7>\left(\frac{1}{243}\right)^7\) mà \(\left(\frac{1}{243}\right)^7>\left(\frac{1}{243}\right)^6\)

Nên \(\left(\frac{1}{80}\right)^7>\left(\frac{1}{243}\right)^6\)

b) Ta so sánh \(\frac{3}{8}\) với \(\frac{5}{243}\)

Ta có: \(\frac{3}{8}=\frac{3.243}{8.243}=\frac{729}{1944}\)

\(\frac{5}{243}=\frac{5.8}{243.8}=\frac{40}{1944}\)

Suy ra: \(\frac{3}{8}>\frac{5}{243}\)

\(\Rightarrow\left(\frac{3}{8}\right)^5>\left(\frac{5}{243}\right)^5\) mà \(\left(\frac{5}{243}\right)^5>\left(\frac{5}{243}\right)^3\)

Nên \(\left(\frac{3}{8}\right)^5>\left(\frac{5}{243}\right)^3\)

\(a,\left(\frac{1}{8}\right)^7>\left(\frac{1}{81}\right)^7=\left(\frac{1}{3^4}\right)^7=\frac{1}{3^{28}}\)

\(\left(\frac{1}{234}\right)^6=\left(\frac{1}{3^5}\right)^6=\frac{1}{3^{30}}\)

Vì \(\frac{1}{3^{28}}>\frac{1}{3^{30}}\)nên \(\left(\frac{1}{80}\right)^7>\left(\frac{1}{243}\right)^8\)

\(b,\left(\frac{3}{5}\right)^5=\left(\frac{3}{2^3}\right)^5=\frac{243}{2^{15}};\)

\(\left(\frac{5}{243}\right)^3=\left(\frac{5}{3^5}\right)^3=\frac{125}{3^{15}}\)

Chọn phân số \(\frac{243}{3^{15}}\)làm phân số trung gian để so sánh hai phân số trên , ta thấy :

\(\frac{243}{2^{15}}>\frac{243}{3^{15}}>\frac{125}{3^{15}}\)

=> \(\frac{243}{2^{15}}>\frac{125}{3^{15}}\)

Từ đó => \(\left(\frac{3}{8}\right)^5>\left(\frac{5}{243}\right)^3\)

 Theo  thứ tự nhé

a) <

b) <

c) >

a) \(\left(\frac{1}{80}\right)^7>\left(\frac{1}{81}\right)^7=\left(\frac{1}{3^4}\right)^7=\frac{1}{3^{4.7}}=\frac{1}{3^{28}}\)

\(\left(\frac{1}{243}\right)^6=\left(\frac{1}{3^5}\right)^6=\frac{1}{3^{3.6}}=\frac{1}{3^{30}}\)

Vì \(\frac{1}{3^{28}}< \frac{1}{3^{30}}\left(3^{28}< 3^{30}\right)\)

Nên \(\left(\frac{1}{80}\right)^7< \left(\frac{1}{243}\right)^6\)

b) \(\left(\frac{3}{8}\right)^5=\frac{3^5}{\left(2^3\right)^5}=\frac{243}{2^{3.5}}=\frac{243}{2^{15}}>\frac{243}{3^{15}}>\frac{125}{3^{15}}\)

\(=\frac{5^3}{\left(3^5\right)^3}=\frac{5^3}{3^{5.3}}=\frac{5^3}{3^{15}}=\left(\frac{5}{243}\right)^3\)

\(\Rightarrow\left(\frac{3}{8}\right)^5>\left(\frac{5}{243}\right)^3\)

a lớn hơn hay sao ý

B lớn hơn A nha bạn 

k cho mk nha bạn