Question

是二次函数,不是一元二次方程.

Answer 1

y＝ax^2+bx+c

= a(x^2+bx/a+c/a)

= a(x^2+bx/a+( b/2a)^2-( b/2a)^2+c/a)

= a(x^2+bx/a+( b/2a)^2)+ (4ac-b^2)/4a

=a(x+b/2a)^2+ (4ac-b^2)/4a