Tìm giá trị của A : A = 1/99 – 1/99×98 – 1/98×97 – …. – 1/3×2 – 1/2×1 26/07/2021 Bởi Audrey Tìm giá trị của A : A = 1/99 – 1/99×98 – 1/98×97 – …. – 1/3×2 – 1/2×1
`A = 1/99 – 1/99.98 – 1/98.97 – … – 1/3.2 – 1/2.1` `A = 1/99 – ( 1/1.2 + 1/2.3 + … + 1/98.99 )` `A = 1/99 – ( 1 – 1/2 + 1/2 – 1/3 + … + 1/98 – 1/99 )` `A = 1/99- ( 1 -1/99 )` `A = 1/99 – 98/99` `A = -97/99` Bình luận
Đáp án: A = $\frac{-97}{99}$ Giải thích các bước giải: A = $\frac{1}{99}$ – $\frac{1}{99.98}$ – $\frac{1}{98.97}$ -…..- $\frac{1}{3.2}$ – $\frac{1}{2.1}$ A = $\frac{1}{99}$ – ( $\frac{1}{2.1}$ + $\frac{1}{3.2}$ + …… $\frac{1}{98.97}$ + $\frac{1}{99.98}$ ) A = $\frac{1}{99}$ – ( 1 – $\frac{1}{2}$ + $\frac{1}{2}$ – $\frac{1}{3}$ +……..+ $\frac{1}{97}$ – $\frac{1}{98}$ + $\frac{1}{98}$ – $\frac{1}{99}$ ) A = $\frac{1}{99}$ – ( 1 – $\frac{1}{99}$ ) A = $\frac{1}{99}$ – $\frac{98}{99}$ A = $\frac{-97}{99}$ Bình luận
`A = 1/99 – 1/99.98 – 1/98.97 – … – 1/3.2 – 1/2.1`
`A = 1/99 – ( 1/1.2 + 1/2.3 + … + 1/98.99 )`
`A = 1/99 – ( 1 – 1/2 + 1/2 – 1/3 + … + 1/98 – 1/99 )`
`A = 1/99- ( 1 -1/99 )`
`A = 1/99 – 98/99`
`A = -97/99`
Đáp án:
A = $\frac{-97}{99}$
Giải thích các bước giải:
A = $\frac{1}{99}$ – $\frac{1}{99.98}$ – $\frac{1}{98.97}$ -…..- $\frac{1}{3.2}$ – $\frac{1}{2.1}$
A = $\frac{1}{99}$ – ( $\frac{1}{2.1}$ + $\frac{1}{3.2}$ + …… $\frac{1}{98.97}$ + $\frac{1}{99.98}$ )
A = $\frac{1}{99}$ – ( 1 – $\frac{1}{2}$ + $\frac{1}{2}$ – $\frac{1}{3}$ +……..+ $\frac{1}{97}$ – $\frac{1}{98}$ + $\frac{1}{98}$ – $\frac{1}{99}$ )
A = $\frac{1}{99}$ – ( 1 – $\frac{1}{99}$ )
A = $\frac{1}{99}$ – $\frac{98}{99}$
A = $\frac{-97}{99}$