Question

Tính nhanh:

1/1x2 + 1/2x3 + 1/3x4 +................+ 1/99x100.

Answer 1

Đặt A = 1/1x2 + 1/2x3 + 1/3x4 + .... + 1/99x100

=> A = 1/1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + .... + 1/99 - 1/100

=> A = 1 - 1/100

=> A = 99/100

Answer 2

A=\(\frac{-99}{100}\)

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tốt

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