Question

câu A  4/2.5+4/5.8+.....+4/47.50

Answer 1

A = \(\dfrac{4}{2.5}\) + \(\dfrac{4}{5.8}\)+...+ \(\dfrac{4}{47.50}\)

A = \(\dfrac{4}{3}\).( \(\dfrac{3}{2.5}+\dfrac{3}{5.8}+...+\dfrac{3}{47.50}\))

A = \(\dfrac{4}{3}\).(\(\dfrac{1}{2}\) - \(\dfrac{1}{5}\) + \(\dfrac{1}{5}\) - \(\dfrac{1}{8}\)+...+ \(\dfrac{1}{47}\) - \(\dfrac{1}{50}\))

A = \(\dfrac{4}{3}\).( \(\dfrac{1}{2}\) - \(\dfrac{1}{50}\)) 

A = \(\dfrac{4}{3}\). \(\dfrac{24}{50}\)

A = \(\dfrac{16}{25}\)