6-7 12+9 20-11 30+13 42-

2020-12-03 21:35:45 字数 2046 阅读 6673

1楼:匿名用户

5/6-7/12+9/20-11/30+13/42-15/56+17/72

=(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)

=1/2+1/9

=11/18

2楼:匿名用户

原式=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

=1/2+1/9

=11/18

5/6-7/12+9/20-11/30+13/42-15/56+17/72

3楼:匿名用户

=1/2+1/9

=11/18

4楼:林居巧

分母拆分成连续自然数,合并得5/2-17/9=11/18

5楼:****天蝎

26/63 不知道有没有算错

5/6-7/12+9/20-11/30+13/42-15/56+17/72

6楼:穗子和子一

=1/2+1/9

=11/18

1又3分之1-7/12+9/20-11/30+13/42-15/56+17/72等于多少

7楼:匿名用户

(1+1/3)-7/12+9/20-11/30+13/42-15/56+17/72

=1+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+1/9

=10/9

5/6-7/12+9/20-11/30+13/42-15/56+17/72-19/90=

8楼:匿名用户

5/6-7/12+9/20-11/30+13/42-15/56+17/72-19/90

=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-(1/9+1/10)

=1/2-1/10

=5/10-1/10

=2/5

注:5/6=5/(2×3)=1/2+1/3

7/12——9/20+11/30——13/42+15/56——17/72 有什么简便方法吗 谢谢

9楼:匿名用户

你认真看每个分母:12=3*4 20=4*5 30=5*6 42=6*7 56=7*8 72=8*9

然后你很快发现:3+4=7 4+5=9 。。。。。

所以你可以用1/3+1/4-(1/4+1/5)-(1/5+1/6)-(1/6+1/7)-(1/8+1/7)-(1/8+1/9) 然后相同去掉 就可以得到答案了

答案是2/9

1-5/6+7/12-9/20+11/30-13/42+15/56-17/72+19/90=?简便运算

10楼:匿名用户

1-5/6+7/12-9/20+11/30-13/42+15/56-17/72+19/90

=1/6+7/12-9/20+11/30-13/42+15/56-17/72+19/90

=1/2+1/10

=(5+1)/10

=6/10

=3/5

3/2-5/6+7/12-9/20+11/30-13/42+15/56-17/72=

11楼:

3/2-5/6+7/12-9/20+11/30-13/42+15/56-17/72

=(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)-(1/8+1/9)

=1-1/9

=8/9

6-7 12+9 20-11 30+13

1楼 匿名用户 5 6 7 12 9 20 11 30 13 42 1 4 9 20 11 30 13 42 1 4 1 12 13 42 1 3 13 42 9 14 5 6 7 12 9 20 11 30 13 42 15 56 17 72 19 90 2楼 匿名用户 5 6 7 12 9 20...