Toán Chứng tỏ răng: 9/2.5+9/5.8+9/8.11+………+9/29.32 >1 31/08/2021 By Peyton Chứng tỏ răng: 9/2.5+9/5.8+9/8.11+………+9/29.32 >1
`9/(2.5)+9/(5.8)+9/(8.11)+………+9/(29.32)` `= 3 . (3/(2.5)+3/(5.8)+3/(8.11)+………+3/(29.32))` `= 3 . (1/2 – 1/5 + 1/5 – 1/8 + 1/8 – 1/11 + …+1/29 – 1/32)` `= 3 . (1/2-1/32)` `= 3. 15/32` `= 45/32 > 1` Vậy `9/(2.5)+9/(5.8)+9/(8.11)+………+9/(29.32) > 1` (Chúc bạn học tốt) Trả lời
$\frac{9}{2.5}$ + $\frac{9}{5.8}$ + $\frac{9}{8.11}$ + … + $\frac{9}{29.32}$ = 3.$\frac{3}{2.5}$ + 3.$\frac{3}{5.8}$ + 3.$\frac{3}{8.11}$ + … + 3.$\frac{3}{29.32}$ = 3.($\frac{1}{2}$ – $\frac{1}{5}$ + $\frac{1}{5}$ – $\frac{1}{8}$ + $\frac{1}{8}$ – $\frac{1}{11}$ + … + … $\frac{1}{29}$ – $\frac{1}{32}$) = 3.($\frac{1}{2}$ – $\frac{1}{32}$) = 3.($\frac{16}{32}$ – $\frac{1}{32}$) = 3.$\frac{15}{32}$ = $\frac{45}{32}$ mà $\frac{45}{32}$ = 1$\frac{13}{32}$ mà 1$\frac{13}{32}$ > 1 ⇒$\frac{9}{2.5}$ + $\frac{9}{5.8}$ + $\frac{9}{8.11}$ + … + $\frac{9}{29.32}$ > 1 Trả lời
`9/(2.5)+9/(5.8)+9/(8.11)+………+9/(29.32)`
`= 3 . (3/(2.5)+3/(5.8)+3/(8.11)+………+3/(29.32))`
`= 3 . (1/2 – 1/5 + 1/5 – 1/8 + 1/8 – 1/11 + …+1/29 – 1/32)`
`= 3 . (1/2-1/32)`
`= 3. 15/32`
`= 45/32 > 1`
Vậy `9/(2.5)+9/(5.8)+9/(8.11)+………+9/(29.32) > 1`
(Chúc bạn học tốt)
$\frac{9}{2.5}$ + $\frac{9}{5.8}$ + $\frac{9}{8.11}$ + … + $\frac{9}{29.32}$
= 3.$\frac{3}{2.5}$ + 3.$\frac{3}{5.8}$ + 3.$\frac{3}{8.11}$ + … + 3.$\frac{3}{29.32}$
= 3.($\frac{1}{2}$ – $\frac{1}{5}$ + $\frac{1}{5}$ – $\frac{1}{8}$ + $\frac{1}{8}$ – $\frac{1}{11}$ + … + … $\frac{1}{29}$ – $\frac{1}{32}$)
= 3.($\frac{1}{2}$ – $\frac{1}{32}$)
= 3.($\frac{16}{32}$ – $\frac{1}{32}$)
= 3.$\frac{15}{32}$
= $\frac{45}{32}$
mà $\frac{45}{32}$ = 1$\frac{13}{32}$
mà 1$\frac{13}{32}$ > 1
⇒$\frac{9}{2.5}$ + $\frac{9}{5.8}$ + $\frac{9}{8.11}$ + … + $\frac{9}{29.32}$ > 1