Tính A = 81.\(\frac{12-\frac{12}{7}-\frac{12}{289}-\frac{12}{85}}{4-\frac{4}{7}-\frac{4}{289}-\frac{4}{85}}\).\(\frac{121212}{818181}\)
B = \(\frac{5\left(2^2.3^2\right)^9\left(2^2\right)^6-2\left(2^2.3\right)^{14}.3^4}{5.2^{28}.3^{18}-7.2^{19}.3^{18}}\)