Sos , giúp em với ạ , lớp 7 sgk cánh diều , bài 3 lũy thừa

Đáp án:

$\begin{array}{l}
c){\left( {\dfrac{3}{7}} \right)^{21}}:{\left( {\dfrac{9}{{49}}} \right)^6}\\
 = {\left( {\dfrac{3}{7}} \right)^{21}}:{\left( {\dfrac{3}{7}} \right)^{2.6}}\\
 = {\left( {\dfrac{3}{7}} \right)^{21}}:{\left( {\dfrac{3}{7}} \right)^{12}}\\
 = {\left( {\dfrac{3}{7}} \right)^{21 - 12}}\\
 = {\left( {\dfrac{3}{7}} \right)^9}\\
d){9.3^3}.\dfrac{1}{{81}}{.3^2}\\
 = {3^2}{.3^3}.\dfrac{1}{{{3^4}}}{.3^2}\\
 = {3^{2 + 3 - 4 + 2}}\\
 = {3^3}\\
 = 27\\
e){3^2}{.2^5}.{\left( {\dfrac{2}{3}} \right)^2}\\
 = {3^2}{.2^5}.\dfrac{{{2^2}}}{{{3^2}}}\\
 = {2^7}\\
 = 128\\
a)\dfrac{{{{45}^{10}}{{.5}^{20}}}}{{{{75}^{15}}}}\\
 = \dfrac{{{{\left( {{3^2}.5} \right)}^{10}}{{.5}^{20}}}}{{{{\left( {{{3.5}^2}} \right)}^{15}}}}\\
 = \dfrac{{{3^{20}}{{.5}^{10}}{{.5}^{20}}}}{{{3^{15}}{{.5}^{30}}}}\\
 = \dfrac{{{3^{15}}{{.5}^{30}}}}{{{5^{30}}}}\\
 = {3^{15}}\\
b)\dfrac{{{2^{15}}{{.9}^3}}}{{{6^6}{{.8}^3}}}\\
 = \dfrac{{{2^{15}}.{{\left( {{3^2}} \right)}^3}}}{{{2^6}{{.3}^6}.{{\left( {{2^3}} \right)}^3}}}\\
 = \dfrac{{{2^{15}}{{.3}^6}}}{{{2^6}{{.3}^6}{{.2}^9}}}\\
 = 1
\end{array}$