:



:

1-
2-
3-
4-
5-
6-
7-
8-

:



:

1-
2-
3-
4-

: :



.

=
:

1 2
ǿ

:

=
- = 2-1=1
= + =
1+2=3


:

3 2

= -
3 - 2 = 1
=

- =
2 - 1=1