有向數加減

Worksheets can be downloaded at

https://www.dropbox.com/s/flu1zuagin6k1xr/directed_num1_11-12.doc

http://www.geogebratube.org/material/show/id/13662 (Download GeoGebra file)

http://www.geogebratube.org/material/show/id/13663 (Download GeoGebra file)

Worksheets can be downloaded at

https://www.dropbox.com/s/p4eva4bpjd1vjcs/directed_num2_11-12.doc