2 câu trả lời
`1/2+5/6+11/12+19/20+29/30+41/42+55/56`
`=1-1/(1.2)+1-1/(2.3)+1-1/(3.4)+1-1/(4.5)+1-1/(5.6)+1-1/(6.7)+1-1/(7.8)`
`=7-(1/(1.2)+1/(2.3)+..+1/(7.8))`
`=7-(1-1/2+1/2-1/3+...+1/7-1/8)`
`=7-(1-1/8)`
`=56/8-7/8`
`=49/8`
Đáp án:
`1/2+5/6+11/12+19/20+29/30+41/42+55/56=49/8`
Giải thích các bước giải:
`1/2+5/6+11/12+19/20+29/30+41/42+55/56`
`=1-1/2+1-1/6+1-1/12+1-1/20+1-1/30+1-1/42+1-1/56`
`=(1+1+1+1+1+1+1)-(1/2+1/6+1/12+1/20+1/30+1/42+1/56)`
`=1.7-(1/(1.2)+1/(2.3)+1/(3.4)+1/(4.5)+1/(5.6)+1/(6.7)+1/(7.8))`
`=7-(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)`
`=7-(1/1-1/8)`
`=7-(8/8-1/8)`
`=7-7/8`
`=56/8-7/8`
`=49/8`
