Đáp án:
Đặt `A = 1 + 1/2 + 1/3 + 1/4 + ........... + 1/31 + 1/32`
`= (1 + 1/2 + 1/3 + ...... + 1/6) + (1/7 + 1/8+ ...... +1/12) + ...... + (1/25 + 1/26 + 1/27 + 1/28) + (1/29+ 1/30 + 1/31 + 1/32)`
`⇒A> (1 + 1/2 + 1/3 + ..... +1/6) + (1/12 + 1/12 + ..... +1/12) + ....... + (1/28 + 1/28 + 1/28 + 1/28) + (1/32 + 1/32 + 1/32+ 1/32)`
`= 49/20 + 1/2 + 1/3 + 1/4 + 1/7 + 1/8`
`=3193/840> 2940/840 = 7/2`
`⇒A>7/2`( đpcm)
`text{ XIN HAY NHẤT NHA}`
@toanisthebest