a^2 + b^2 + c^2 - 4a + 4b - 6c ≤ -17 (a - 2)^2 -4 + (b + 2)^2 -4 + (c - 3)^2 -9 ≤-17 (a - 2)^2 + (b + 2)^2 + (c - 3)^2 ≤ 0 所以 (a - 2)^2 + (b + 2)^2 + (c - 3)^2 = 0 (a - 2)^2 = (b + 2)^2 = (c - 3)^2 = 0 a = 2 b = -2 c = 3 a + b + c = 3 先把代数式化简 结果为 b/2 = -2/2 = -1