y=ax²+bx+c化为一般形式 y=a(x+2a分之b）²+4a分之4ac-b²y=a(x²+bx/a)+c=a(x²+2×(b/2a)×x+(b/2a)²)+c-a×(b/2a)²;=a(x+b/2a)²+c-b²/4a;=a(x+b/2a)²+(4ac-b²...