第1个回答 2012-12-15
解:设点C'为(xo,yo)
依题意,有
4/3*9+3b+c=0
c=4
=>b=-16/3
=>抛物线为:y=4x²/3-16x/3+4=4/3*(x²-4x+3)=4/3*(x-1)(x-3)
=>C点为(1,0)
对于直线AB,其斜率k(AB)=-4/3
=>l(AB):y=-4/3*(x-3)
点C'与点C关于直线AB对称,则直线AB必垂直平分C'C,两直线的交点为([xo+1]/2,yo/2)
由(-4/3)*yo/(xo-1)=-1,yo/2=-4/3*[(xo+1)/2-3]
=>xo=29/13,yo=12/13
=>C'点为(29/13,12/13)