當(dāng)x=2/3與x=1/3時(shí),y的值相等
所以對(duì)稱軸是x=(2/3+1/3)/2=1/2
y=a(x-1)^2+h
x=1時(shí),y=-2;
-2=a*0+h
h=-2
y=a(x-1)^2-2
當(dāng)x=-1時(shí),y=20;
20=a*(-2)^2-2
a=11/2
y=11(x-1)^2/2-2
=11x^2/2-11x+7/2
a=11/2,b=-11,c=7/2