頂點(diǎn)坐標(biāo)是(1.16),有
X=-B/2A=1,B=-2A.
Y=(4AC-B^2)/4A=16,B^2-4AC=-4*16A.
解得,C=16+4A.
|X2-X1|=AB=8,
X1^2+X2^2-2X1*X2=64,
(X1+X2)^2-4X1*X2=64.
X1+X2=-B/A,X1*X2=C/A.
(-B/A)^2-4C/A=64,
B^2-4AC=64A^2,B^2-4AC=-4*16A,
-4*16A=64A^2,(A≠0,)
A=-1.B=-2A=2.
C=16+4A=16-4=12.
拋物線的表達(dá)式為:Y=-X^2+2X+12.