初三数学二次函数一般式怎么变成顶点式

Question

如题所述

Answer 1

y=ax�0�5+bx+c，化为顶点式是：y=a(x+b/2a)�0�5+(4ac-b�0�5)/4a
配方过程如下：y=ax�0�5+bx+c
=a(x�0�5+bx/a)+c
=a(x�0�5+bx/a+b�0�5/4a�0�5-b�0�5/4a�0�5)+c
=a(x+b/2a)�0�5-b�0�5/4a+c
=a(x+b/2a)�0�5+(4ac-b�0�5)/4a

Answer 2

y=ax²+bx+c，化为顶点式是：y=a(x+b/2a)²+(4ac-b²)/4a
配方过程如下：y=ax²+bx+c
=a(x²+bx/a)+c
=a(x²+bx/a+b²/4a²-b²/4a²)+c
=a(x+b/2a)²-b²/4a+c
=a(x+b/2a)²+(4ac-b²)/4a

Answer 3

十字相乘法啊