Question

[꧁s̸ói̸ g̸a̸m̸i̸n̸g̸꧂]

1. Tính nhanh:

M = 1 x 1/2 + 1/2 x 1/3 + 1/3 x 1/4 +...+ 1/99 x 1/100

cíu :))

Answer 1

[Phước Lộc]

\(M=1\times\dfrac{1}{2}+\dfrac{1}{2}\times\dfrac{1}{3}+\dfrac{1}{3}\times\dfrac{1}{4}+...+\dfrac{1}{99}\times\dfrac{1}{100}\)

\(M=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{99}-\dfrac{1}{100}\)

\(M=1-\dfrac{1}{100}\)

\(M=\dfrac{99}{100}\)

Answer 2

[Đỗ quyết Tiến]

??????????

Ko bit làm