Question

y=ax^2+bx+c通过配方成为y=a（x+b/2a）^2+（4ac-b^2)/4a 请问这个怎

Answer 1

y=ax^2＋bx+c

=a(x^2+b/ax)+c

=a[x^2+b/ax+(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-b^2/4a+c

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