Question

（1）先計算下面各題，再看看有什么規(guī)律．

1

2

+

1

3

=

1

2

-

1

3

=

1

3

+

1

4

=

1

3

-

1

4

=

1

4

+

1

5

=

1

4

-

1

5

=
（2）根據(jù)上面的規(guī)律，直接寫出下面各題的得數(shù)．

1

3

+

1

5

=

1

7

-

1

8

=

1

2

+

1

7

=

1

3

-

1

7

=

1

8

+

1

5

=

1

4

-

1

9

=

Answer 1

分析：根據(jù)分數(shù)加減法的計算方法進行計算．

解答：解：

1

2

+

1

3

=

5

6

1

2

-

1

3

=

1

6

1

3

+

1

4

=

7

12

1

3

-

1

4

=

1

12

1

4

+

1

5

=

9

20

1

4

-

1

5

=

1

20

我發(fā)現(xiàn)：分子是1，分母是互質(zhì)數(shù)的兩個分數(shù)相加減，分母的乘積作為分母，分母相加減作為分子．
（2）

1

3

+

1

5

=

8

15

1

7

-

1

8

=

1

56

1

2

+

1

7

=

9

14

1

3

-

1

7

=

4

21

1

8

+

1

5

=

13

40

1

4

-

1

9

=

5

36

．

點評：異分母分數(shù)相加減，先通分，然后再按照同分母分數(shù)的加減法進行計算．