设P1(a,b)
则PP1垂直于对称轴
2x-y+3=0斜率是2
垂直则斜率是-1/2
(b-3)/(a-1)=-1/2
a+2b=7 (1)
且PP1中点在对称轴上
所以
2(1+a)/2-(3+b)/2+3=0
2a-b=-5 (2)
所以
a=-3/5,b=19/5
P1(-3/5,19/5)