✨ 最佳解答 ✨
A^2 -3A -10 = 0
(A-5)(A+2) = 0
(x+2-5)(x+2+2) = 0
(x-3)(x+4) = 0
x = 3 or -4
若共同解為 x = 3,則
x^2 +kx +3k = 0
9 +3k +3k = 0
6k = -9
k = -3/2 (與題目 k 為整數不符)
若共同解為 x = -4,則
x^2 +kx +3k = 0
16 -4k +3k = 0
k = 16
x^2 +16x +48 = 0
(x+4)(x+12) = 0
x = -4 or -12
=> 另一個解為 -12
k = -3/2 (與題目 k 為整數不符)
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