Tìm x biết:
a) \(\frac{1}{5.8}\)+ \(\frac{1}{8.11}\)+ \(\frac{1}{11.14}\)+...+ \(\frac{1}{\left(x-2\right).x}\)+ \(\frac{1}{x\left(x+2\right)}\)= \(\frac{101}{1540}\).
b) 1+ \(\frac{1}{3}\)+ \(\frac{1}{6}\)+ \(\frac{1}{10}\)+...+ \(\frac{1}{x\left(x+1\right):2}\)= 1\(\frac{1991}{1993}\).