Think about it, this intersection must be on a parabola, then x >；; 0

I see it this way.

First, the center of the circle is (4,0), so 0.

More than four, there are only two intersections left ~ ~

Then, two consecutive columns (x-4) 2+x = r 2, namely x 2-7x+ 16-r 2 = 0.

Discriminant is greater than 0