Question

Tính: 5/3+5/12+5/48+....+5/768+5/3072

Answer 1

            A =          \(\dfrac{5}{3}\) + \(\dfrac{5}{12}\) + \(\dfrac{5}{48}\) +......+ \(\dfrac{5}{768}\) + \(\dfrac{5}{3072}\)

       4\(\times\)A = \(\dfrac{20}{3}\) + \(\dfrac{5}{3}\) + \(\dfrac{5}{12}\) + \(\dfrac{5}{48}\)+........+ \(\dfrac{5}{768}\)

4\(\times\) A - A  =  \(\dfrac{20}{3}\) -  \(\dfrac{5}{3072}\)

          3A =  \(\dfrac{6855}{1024}\)

            A = \(\dfrac{6855}{1024}\) : 3

           A  =  \(\dfrac{2275}{1024}\)