二次函数公式法
作者：互联网
\[\Large y=ax^2+bx+c
\]\[\Large y=a(x^2+\dfrac{b}{a}x+\dfrac{c}{a})
\]\[\Large y=a(x^2+2\times x\times \dfrac b {2a}+\dfrac c a)
\]\[\Large y=a[x^2+2x\dfrac b {2a}+(\dfrac b {2a})^2-(\dfrac b {2a})^2+\dfrac c a]
\]\[\Large y=a[(x+\dfrac b {2a})^2-\dfrac{b^2}{4a^2}+\dfrac c a]
\]\[\Large y=a(x+\dfrac b {2a})^2-\dfrac{b^2}{4a}+c
\]\[\Large y=a(x+\dfrac b {2a})^2-\dfrac{b^2}{4a}+\dfrac {4ac}{4a}
\]\[\Large y=a(x+\dfrac b {2a})^2+\dfrac{4ac-b^2}{4a}
\]
因此其顶点坐标为 \(\Large (-\dfrac b {2a},\dfrac{4ac-b^2}{4a})\)
标签：函数,二次,dfrac,4ac,times,Large,2a,公式,4a 来源： https://www.cnblogs.com/zhangtingxi/p/16473421.html