並前往https://math.ymhs.tyc.edu.tw/masterchen/chenjt99/ScrClass/1091/%E9%AB%98%E4%BA%8C%E7%BF%92%E4%BD%9C3A/ch2/2-4%20%E6%8C%87%E6%95%B8%E8%88%87%E5%B0%8D%E6%95%B8%E5%87%BD%E6%95%B8%E7%9A%84%E6%87%89%E7%94%A8.pdf
