並前往http://www.nowforyou.com/math/%E5%82%99%E8%AA%B2/6-2-2%E7%AE%97%E8%A1%93%E5%B9%B3%E5%9D%87%E6%95%B8%E3%80%81%E4%B8%AD%E4%BD%8D%E6%95%B8%E8%88%87%E7%9C%BE%E6%95%B8.pdf
