Tính giá trị biểu thức
A=\(\dfrac{\left(1+17\right)\cdot\left(1+\dfrac{17}{2}\right)\cdot\left(1+\dfrac{17}{3}\right)....\left(1+\dfrac{17}{19}\right)}{\left(1+19\right)\cdot\left(1+\dfrac{19}{2}\right)\cdot\left(1+\dfrac{19}{3}\right)....\left(1+\dfrac{19}{17}\right)}\)