AQ中点M的坐标(x,y),则Q坐标是(2x-1,2y)
Q坐标代入椭圆方程:
(2x-1)^2/4+(2y)^2=1
4x^2-4x+1+16y^2=4
即轨迹方程是:4x^2+16y^2-4x-3=0