二次函數解析式怎麼配方？

12-03

(???‵‵)老師教的都還肥去惹。。QUQ

$egin{eqnarray*} f(x) = ax^{2}+bx+c \ = aleft[x^{2}+frac{b}{a}x+frac{c}{a} ight] \ = aleft[x^{2}+frac{b}{a}x+left(frac{b}{2a} ight)^{2}-left(frac{b}{2a} ight)^{2}+frac{c}{a} ight] \ = aleft[left(x+frac{b}{2a} ight)^{2}+frac{4ac-b^{2}}{4a^{2}} ight] \ = aleft(x+frac{b}{2a} ight)^{2}+frac{4ac-b^{2}}{4a} end{eqnarray*}$