This topic examines how to find the analytic expressions of quadratic function and linear function by undetermined coefficient method, the judgment and properties of similar triangles, the judgment and properties of parallel lines, the properties of isosceles triangle, the solution of fractional equation, the internal angle and theorem of triangle, the properties of rotation, and the intersection of parabola and straight line. , comprehensive and difficult. Prove that ∠POD=∠BAO, and then prove that the triangle BAO is similar to the triangle POD.

As shown in the figure, parabola y=a(x-m)? (where m> 1) intersects its symmetry axis l at point p, and the y axis intersects at point a (0, m- 1). Connect and extend PA, PO, X axis and parabola at points B and C respectively, and connect BC. The symmetry point of point C about the straight line L is c', which connects PC', that is, there is PC'=PC.

(1) The analytical formula of this parabola is _ _ _ _ _ _ (expressed by the formula containing m);

(2) Verification: BC//y axis;

(3) If the point B' falls on the line BC', find the value of m at this time.