Question

[quang trung]

Tinh nhanh ( ai nhanh nhat minh click  cho)

X= 3 + 3  + 3  + ... + 3   

      4    28   70           208

(Cau tren la phan so)

Answer 1

[Nguyễn Đình Dũng]

X = 3/4 + 3/28 + 3/70 + .... + 3/208

X = 3/1.4 + 3/4.7 + 3/7.10 + ... + 3/13.16

X = 1 - 1/4 + 1/4 - 1/7 + 1/7 - 1/10 + .... + 1/13 - 1/16

X = 1 - 1/16

X = 15/16