It is known that the circle C passes through two points a (3.2) and B (1.6), and the center of the circle is on the straight line y = 2x (1): find the equation of circle C（ It is known that the circle C passes through two points a (3.2) and B (1.6), and the center of the circle is on the straight line y = 2x (1): find the equation of the circle C (2): if the straight line L passes through P (1.3) and is tangent to the circle C, find the equation of the straight line L

It is known that the circle C passes through two points a (3.2) and B (1.6), and the center of the circle is on the straight line y = 2x (1): find the equation of circle C（ It is known that the circle C passes through two points a (3.2) and B (1.6), and the center of the circle is on the straight line y = 2x (1): find the equation of the circle C (2): if the straight line L passes through P (1.3) and is tangent to the circle C, find the equation of the straight line L

(1) ∵ the center of the circle is on y = 2x, if the abscissa of the center is a, then the ordinate is 2a, that is, the center of the circle is C (a, 2a) and Ca & # 178; = CB & # 178; = R & # 178; then (A-3) &# 178; + (2a-2) &# 178; = (A-1) &# 178; + (2a-6) &# 178; the solution is a = 2, then the center coordinate is (2,4) so that