Question

计算、观察、思考． 1 2 × 1 3 =	1 5 × 1 6 =	1 7 × 1 8 =
1 2 - 1 3 =	1 5 - 1 6 =	1 7 - 1 8 =

Answer 1

1 2 × 1 3 = 1 6	1 5 × 1 6 = 1 30	1 7 × 1 8 = 1 56
1 2 - 1 3 = 1 6	1 5 - 1 6 = 1 30	1 7 - 1 8 = 1 56 ．

通过计算，发现：

1

2

×

1

3

=

1

2

-

1

3

，

1

5

×

1

6

=

1

5

-

1

6

，

1

7

×

1

8

=

1

7

-

1

8

．
通过观察，两个分数的分母是两个连续的自然数，它们的乘积可以拆分成两个分数相减的形式．