Pls make ur qsn clearer in 1)
2) Point of interesection is (1,-4).
Eqn of any line through this is y+4=m(x-1)
Equating this with parabola eqn y2=4x, we get y1+y22=k=2m
Similalrly we have the eqn m2x2+(m+4)2-(2m2+8m)x=4x, we can thus eleminate 'm' from these 2 equations, and get reqd locus........
Nudge if prob not cleared.