OP^2=a^2+a^2/4=5a^2/4

The distance from p to the straight line x+2y-3=0 d=la-a-3l/ root number (1+4)=3/ root number 5=3 root number 5 /5.

So the root number 5 a/2=3 and the root number 5/5.

a=6/5

P(6/5，-3/5)