-1+5/6-7/12+9/20-11/30+13/42-15/56+17/72
来源:百度知道 编辑:UC知道 时间:2024/07/08 22:15:50
讲的细一点,加分,不少哦!!!!!
把所有分数都拆开来
5/6=1/2+1/3
7/12=1/3+1/4
9/20=1/4+1/5
11/30=1/5+1/6
13/42=1/6+1/7
15/56=1/7+1/8
17/72=1/8+1/9
然后代入原式得:
原式=-1+(1/2+1/3)-(1/3+1/4)+(1/4+1/5)-(1/5+1/6)+(1/6+1/7)-(1/7+1/8)+(1/8+1/9)
=-1+1/2+1/3-1/3-1/4+1/4+1/5-1/5-1/6+1/6+1/7-1/7-1/8+1/8+1/9
观察发现除了-1,1/2和1/9外,其它的都正负相抵了
所以原式=-1+1/2+1/9=(-18+9+2)/18=-7/18
把所有分数都拆开来
5/6=1/2+1/3
7/12=1/3+1/4
9/20=1/4+1/5
11/30=1/5+1/6
13/42=1/6+1/7
15/56=1/7+1/8
17/72=1/8+1/9
然后代入原式得:
原式=-1+(1/2+1/3)-(1/3+1/4)+(1/4+1/5)-(1/5+1/6)+(1/6+1/7)-(1/7+1/8)+(1/8+1/9)
=-1+1/2+1/3-1/3-1/4+1/4+1/5-1/5-1/6+1/6+1/7-1/7-1/8+1/8+1/9
观察发现除了-1,1/2和1/9外,其它的都正负相抵了
所以原式=-1+1/2+1/9=(-18+9+2)/18=-7/18
2/1X+12/1X+7/1X+6/1X+5+4=X
1/1*2+1/2*3+1/3*4+1/4*5+1/5*6+1/6*7+1/7*8+1/8*9+1/9*10+1/10*11+1/11*12+1/12*13+1/13*14+1/14*15=?
1又1/2-5/6+7/12-9/20+11/30-13/42+15/56=?
求解一道小学数学题1+2*1/6+3*1/12+4*1/20+5*1/3+6*1/42+7*1/56+8*1/72+9*1/90
1-5/6+7/12-9/20+11/30-13/42+15/56-17/72简便方法怎么算
用简便方法算:1-5/6+7/12-9/20+11/30-15/42+/17/56
1/(2/3)/(3/4)/(4/5)/(5/6)/(6/7)/(7/8)
计算1/6 x+1/12 x+1/7 x+5+1/2 x+4=x
1/2,1/2,5/12,7/20,( ).找规律填数,
5x-1/6=7/3