What is the Combined equation of normal to parabola at the focii? For EXAMPLE in the following sum

y^2 = 4ax

end point of L.R.

L (a, 2a) , L’ (a,– 2a)

t1 = 1, t2 = – 1

eqn of normals are

y + t x = 2at + at3

y + x = 3a

y – x = – 3a

combined equation of normal’s are

NOW THIS MY DOUBT WHY WOULD WE GET SUCH A STEP

[y + (x – 3a)] [y – (x – 3a)] = 0

-----> THIS [Eq1*Eq2=0] ???