(1)由题设知a=2,b=
3
椭圆C的方程
+x2 4
=1y2 3
(2)由点差法知PQ的中垂线交x轴于T(
,0)1 4
设M(x1,y1),N(x2,y2),直线MN:x=my+1与椭圆联立可得(3m2+4)y2+6my-9=0|y1?y2|2=
+36m2
(3m2+4)2
=14436 3m2+4
m2+1 (3m2+4)2
令t=m2+1≥1,则|y1?y2|2=144
=144t (3t+1)2
≤91 9t+
+61 t
故Smax=
×1 2
×3=3 4
9 8