Toán 1/2 + 1/6 +1/12+1/20+1/30+ ……..+ 1/9900 nhanh nhé 25/09/2021 By Madeline 1/2 + 1/6 +1/12+1/20+1/30+ ……..+ 1/9900 nhanh nhé
Đáp án: Giải thích các bước giải: $\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+…+\dfrac{1}{9900}$ $ $ $=\dfrac{1}{1.2}+\dfrac{1}{2.3}+\dfrac{1}{3.4}+…+\dfrac{1}{99.100}$ $ $ $=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+…+\dfrac{1}{99}-\dfrac{1}{100}$ $ $ $=1-\dfrac{1}{100}$ $ $ $=\dfrac{99}{100}$ Trả lời
=$\frac{2}{1×2}$ – $\frac{1}{1×2}$ + 3/(2×3) – 2/(2×3) + ….. + 100/(100×99) – 99/(100×99) =1 – 1/100=99/100 Trả lời
Đáp án:
Giải thích các bước giải:
$\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+…+\dfrac{1}{9900}$
$ $
$=\dfrac{1}{1.2}+\dfrac{1}{2.3}+\dfrac{1}{3.4}+…+\dfrac{1}{99.100}$
$ $
$=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+…+\dfrac{1}{99}-\dfrac{1}{100}$
$ $
$=1-\dfrac{1}{100}$
$ $
$=\dfrac{99}{100}$
=$\frac{2}{1×2}$ – $\frac{1}{1×2}$ + 3/(2×3) – 2/(2×3) + ….. + 100/(100×99) – 99/(100×99)
=1 – 1/100=99/100