✔ 最佳答案
可以代入 α 去兩條式度,因為佢係根
α^2 - 4α + k = 0 ... (1)
2α^2 - 3α + k = 0 ... (2)
(2) - 2 x (1): 5α - k = 0
α = k/5
將 α = k/5 代入 (1) 中,
(k/5)^2 - 4(k / 5) + k = 0
k^2 - 20k + 25k = 0
k^2 + 5k = 0
k (k + 5) = 0
k = 0 或 k = -5.
2007-10-13 20:26:30 補充:
(2) - 2 x (1) 加減消元法睇唔明可以分開來做2 x (1): 2(α^2 - 4α k) = 2(0)2α^2 - 8α 2k = 0 ... (3)
2007-10-13 20:27:16 補充:
(2) - (3) : 5α - k = 0跟住就係一樣的步驟