the slope of the tangents to the parabola is given by:
let us denote the x coordinate (where it touches the parabola) of the first line as: and that of the second line as , now we're told that the two tangents are perpendicular thus:
the equations of the two lines are:
we know that the two lines intersect at (1,0), thus:
so we've got two equation in two unknowns , find them and then finding n is trivial...