Toán Tính nhanh 1/2+1/6+1/12+1/20+1/30+1/42+1/56 12/07/2021 By Amara Tính nhanh 1/2+1/6+1/12+1/20+1/30+1/42+1/56
Đáp án + Giải thích các bước giải: `1/2+1/6+1/12+1/20+1/30+1/42+1/56` `= 1/[1xx2]+1/[2xx3]+1/[3xx4]+1/[4xx5]+1/[5xx6]+1/[6xx7]+1/[7xx8]` `= 1 – 1/2 + 1/2 – 1/3 + … + 1/7 – 1/8` `= 1 – 1/8` `= 7/8` Trả lời
`1/2 + 1/6 + 1/12 + 1/20 + 1/30 + 1/42 + 1/56` `= 1/{1 × 2} + 1/{2 × 3} + 1/{3 × 4} + 1/{4 × 5} + 1/{5 × 6} + 1/{6 × 7} + 1/{7 × 8}` `= 1/1 × ( 1/1 – 1/2 + 1/2 – 1/3 + 1/3 – 1/4 + 1/4 – 1/5 + 1/5 – 1/6 + 1/6 – 1/7 + 1/7 – 1/8 )` `= 1/1 × ( 1/1 + 1/2 – 1/2 + 1/3 – 1/3 + 1/4 – 1/4 + 1/5 – 1/5 + 1/6 – 1/6 + 1/7 – 1/7 – 1/8 )` `= 1/1 × ( 1/1 + 0 + 0 + 0 + 0 + 0 + 0 – 1/8 )` `= 1/1 × ( 1/1 – 1/8 )` `= 1/1 × 7/8` `= 7/8` `#dtkc` Trả lời
Đáp án + Giải thích các bước giải:
`1/2+1/6+1/12+1/20+1/30+1/42+1/56`
`= 1/[1xx2]+1/[2xx3]+1/[3xx4]+1/[4xx5]+1/[5xx6]+1/[6xx7]+1/[7xx8]`
`= 1 – 1/2 + 1/2 – 1/3 + … + 1/7 – 1/8`
`= 1 – 1/8`
`= 7/8`
`1/2 + 1/6 + 1/12 + 1/20 + 1/30 + 1/42 + 1/56`
`= 1/{1 × 2} + 1/{2 × 3} + 1/{3 × 4} + 1/{4 × 5} + 1/{5 × 6} + 1/{6 × 7} + 1/{7 × 8}`
`= 1/1 × ( 1/1 – 1/2 + 1/2 – 1/3 + 1/3 – 1/4 + 1/4 – 1/5 + 1/5 – 1/6 + 1/6 – 1/7 + 1/7 – 1/8 )`
`= 1/1 × ( 1/1 + 1/2 – 1/2 + 1/3 – 1/3 + 1/4 – 1/4 + 1/5 – 1/5 + 1/6 – 1/6 + 1/7 – 1/7 – 1/8 )`
`= 1/1 × ( 1/1 + 0 + 0 + 0 + 0 + 0 + 0 – 1/8 )`
`= 1/1 × ( 1/1 – 1/8 )`
`= 1/1 × 7/8`
`= 7/8`
`#dtkc`