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F.6 軌跡 1

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10.http://i1054.photobucket.com/albums/s486/monita19950826/003_zps82db42dd.png

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10(a)(i) 代L1入Cx^2 + (mx + 3)^2 + 12x - 10(mx + 3) + 53 = 0(1 + m^2)x^2 + (12 - 4m)x + 32 = 0判別式 = 0(12 - 4m)^2 - 4(1 + m^2)(32) = 0(3 - m)^2 - 8(1 + m^2) = 0m^2 - 6m + 9 - 8m^2 - 8 = 07m^2 + 6m - 1 = 0(ii) (7m - 1)(m + 1) = 0m = -1(b)(i) L2的斜率是1(ii) 設L2:y = x + c代入C:x^2 + (x + c)^2 + 12x - 10(x + c) + 53 = 02x^2 + (2c + 2)x + c^2 - 10c + 53 = 0判別式 = 0(2c + 2)^2 - 8(c^2 - 10c + 53) = 04c^2 + 8c + 4 - 8c^2 + 80c - 424 = 0c^2 - 22c + 105 = 0(c - 15)(c - 7) = 0c = 7 或 15L2的方程為y = x + 7 或 y = x + 15

其他解答:D1B39E804036C6BD
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