跟老师要答案得了.4a^2(-2)^2 + 4a(-2) + b - 8 = 0,b = -8,16a^2 - 8a - 16 = 0,2a^2 - a - 2 = 0,1^2 + 4*2*2 = 17.a = [1 - (17)^(1/2)]/4 或 a = [1 + (17)^(1/2)]/4 a是实数时,由 4a^2(-2)^2 + 4a(-2) + b - 8 ...