[填空题]
A quadratic function f can be written in tu a*a2nq v5vs8bf9a .ahe form f(x)=p(xi6)wj- :bp p: rwdyhl0-1)(x-q) .
The graph of y=f(x) has axis of symmetry x=2 and y -intercept at (0,-3) .
1. Find the value of q .
2. Find the value of p .
The line y=k x+6 is a tangent to the graph of y=f(x) .
3. Find the possible values of k .