a)\(\dfrac{\dfrac{2}{3}-}{\dfrac{8}{3}-}\dfrac{\dfrac{2}{5}+}{\dfrac{8}{5}+}\dfrac{\dfrac{2}{7}-}{\dfrac{8}{7}-}\dfrac{\dfrac{2}{9}+}{\dfrac{8}{9}+}\dfrac{\dfrac{2}{11}}{\dfrac{8}{11}}\)
b)\(\left(\dfrac{1}{2}-1\right)\left(\dfrac{1}{3}-1\right)\left(\dfrac{1}{4}-1\right)...\left(\dfrac{1}{50}-1\right)\left(\dfrac{1}{51}-1\right)\)