已知F(1,0),直线方程：
Y/(X-1)=K①
Y²=4X②
①②→K²X²-(2K²+4)X+K²=0
→X1+X2=(4+2K²)/K²③
X1X2=1④
设M(x,y)
2x=③→k²=2/(x-1)⑤
2y=④→k²=4/y²⑥
⑤⑥→2/(x-1)=4/y²