So something like this?:
0=2x^2-8, 8/2=x^2, 4=x^2, x= +2 or -2
y=x^2, x= rad(y):
-2 =rad(y) is nonreal, so 2= rad(y), y=4
x=2, y=4.
Problem is:
equating the tangent line (y) with the parabola (Y) is impossible... y never actually touches Y. They should share no points.