过点P的直线为：y=k(x-4)+2=kx-4k+2代入C：(1+k^2)x^2+4(k-2k^2-1)x+(2-4k)^2+1=0弦坐标为：(x1,y1),(x2,y2), y1=kx1-4k+2, y2=kx2-4k+2由韦达定理：x1+x2=4(2k^2-k+1)/(1+k^2)中点坐标为：（x,y)x=(x1+x2)/2=2(2k...