Question

如图抛物线与x轴相交于B,C两点,与y轴交于点A,P(2a,-4a²+7a+2)(a是实数)在抛物线上,直线y

Answer 1

∵P(2a,-4a²+7a+2)在抛物线上,

∴X=2a,

Y=-(2a)^2+7/2(2a)+2=-X^2+7/2X+2,

令X=0,Y=2,∴A(0,2),

令Y=0,-X^2+7/2X+2=0,

X=-1/2或4,

∴B(-1/2,0)或(4,0),

∴直线AB：Y=4X+2或Y=-1/2X+2.