Tìm x biết :
a) x + \(\frac{4}{5.9}\) +\(\frac{4}{9.13}\) +\(\frac{4}{13.17}\)+ . . . + \(\frac{4}{41.45}\) = −\(-\frac{37}{45}\)
b) \(\frac{5}{1.6}\) +\(\frac{5}{6.11}\) + . . . + \(\frac{5}{\text{(5x+1).(5x+6)}}\) =\(\frac{2015}{2016}\)
c) \(\frac{2}{1.3}\)+\(\frac{2}{3.5}\) +\(\frac{2}{5.7}\) +. . . + \(\frac{2}{x\left(x+2\right)}\) = \(\frac{2017}{2018}\)