1. Tính
a) $\frac{49^{5}.7^{16}}{7^{18}.7^{6}}$
b) $\frac{4^{16}.8^{20}}{2^{14}.32^{15}}$
2. Tìm $x$
a) $\left ( \frac{3}{2}. x +\frac{4}{3} \right )^{2}=\frac{4}{9}$
b) $\left ( \frac{7}{15}-\frac{3}{20}.x \right )^{3}=\frac{-8}{125}$
3. Rút gọn
a) $x ^{n+1}.x ^{n+2}$
b) $x ^{3.( n+4)}\div x^{2( n-1)}$