(1)设P(a,0) Q(0,b) 因为C(5,2) 所以PQ=根号汪凳下a2+b2 CQ=根号下拦陵带25+(2-b)2 CP=根号下(5-a2)+4根简芦据PQ=PC 和勾股定理列等式(2)设C(x,x-3)··························