a) A =\(\dfrac{5\left(31-\dfrac{2}{7}-\dfrac{1}{11}+\dfrac{1}{23}\right)}{13\left(31-\dfrac{2}{7}-\dfrac{1}{11}+\dfrac{1}{23}\right)}+\dfrac{\dfrac{3}{5}+\dfrac{21}{91}-\dfrac{9}{10}}{\dfrac{7}{91}+\dfrac{1}{5}-\dfrac{3}{10}}\)
=\(\dfrac{5}{13}+\dfrac{3\left(\dfrac{1}{5}+\dfrac{7}{91}-\dfrac{3}{10}\right)}{\dfrac{1}{5}+\dfrac{7}{91}-\dfrac{3}{10}}\)
= 5/13 + 3
= 5/13 + 39/13
= 44/13 = 3 5/13 (hỗn số)
b) B =\(\dfrac{2\cdot3\cdot5\cdot2^{14}\cdot3^{29}-5\cdot2^5\cdot7^5\cdot2^{12}}{3^3\cdot2\cdot2^{14}\cdot3^{14}-2^2\cdot3\cdot2^{15}\cdot7^5}\)
=\(\dfrac{2^{15}\cdot3^{30}\cdot5-5\cdot2^{17}\cdot7^5}{2^{15}\cdot3^{30}\cdot3-2^{17}\cdot3\cdot7^5}\)
=\(\dfrac{5\left(2^{15}\cdot3^{30}\cdot5-2^{17}\cdot7^5\right)}{3\left(2^{15}\cdot3^{30}-2^{17}\cdot7^5\right)}\)
= 5/3 = 1 2/3