y=ax²+bx+c=a[x²+ (b/a)x]+c=a[x²+2(b/2a)x]+c=a[x²+2(b/2a)x+(b/2a)²-(b/2a)²]+c=a[(x+b/2a)²-(b/2a)²]+c=a(x+b/2a)²-a(b/2a)²+c=a(x+b/2a)²-b²/4a+c...