x²-x/4=9/4x²-x/4+1/64=9/4+1/64=145/64(x-1/8)²=(±√145/8)²x-1/8=±√145/8x=(1-√145)/8,x=(1+√145)/8
(x-3)²+(y-1)²=25圆心C(3,1)PC=√(1²+2²)=√5所以P在园内弦长最小则垂直于过P的直径所以由勾股定理弦长=2√(r²-PC²)=4√5
