Để olm.vn giúp em nhá
C = \(\dfrac{1}{1.4}\) + \(\dfrac{1}{4.7}\) + \(\dfrac{1}{7.11}\)+...+ \(\dfrac{1}{994.997}\) + \(\dfrac{1}{997.1000}\)
C = \(\dfrac{1}{3}\).( \(\dfrac{3}{1.4}\) + \(\dfrac{3}{4.7}\) + \(\dfrac{3}{7.11}\)+...+ \(\dfrac{3}{994.997}\)+ \(\dfrac{3}{997.1000}\))
C = \(\dfrac{1}{3}\).( \(\dfrac{1}{1}\) - \(\dfrac{1}{4}\) + \(\dfrac{1}{4}\) - \(\dfrac{1}{7}\) + \(\dfrac{1}{7}\)-\(\dfrac{1}{11}\)+...+ \(\dfrac{1}{994}\)- \(\dfrac{1}{997}\)+ \(\dfrac{1}{997}\) - \(\dfrac{1}{1000}\))
C = \(\dfrac{1}{3}\).( \(\dfrac{1}{1}\) - \(\dfrac{1}{1000}\))
C = \(\dfrac{1}{3}\). \(\dfrac{999}{1000}\)
C = \(\dfrac{333}{1000}\)