a(x^2 + b/a * x + c/a) = 0∵ a ≠ 0,∴ x^2 + b/a * x + c/a = 0即 x^2 + b/a * x + (b/2a)^2 + [c/a - (b/2a)^2] = 0则有 (x + b/2a)^2 = (b/2a)^2 - c/a(1) 如果 (b/2a)^2 - c/a < 0,则方程无解,与原题不符,∴(b...[c/a - (b/2a)^2] = 这里是什么意思？从 x^2 + b/a * x + c/a = 0 到 x^2 + b/a * x + (b/2a)^2 + [c/a - (b/2a)^2] = 0相当于 x^2 + b/a * x + c/a +(b/2a)^2 -(b/2a)^2 = 0而已，x^2 + b/a * x + (b/2a)^2放在一起是为了化简方程式，那多加的 (b/2a)^2必须在后面减掉。采纳吧，看我三更半夜还帮你答题哈。。