>>409
y=a(x+b/2a)^2-(b^2)/(4a)+c
cを(4ac)/(4a)の形に直す
y=a{x+(b/2a)}^2-(b^2)/(4a)+(4ac)/(4a)
y=a{x+(b/2a)}^2-(b^2-4ac)/(4a)