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...