解：x²＋y²－2x﹢4y﹢5=0x²－2x+1＋y²﹢4y﹢4=0(x-1)²+(y+2)²=0x-1=0或y+2=0x=1或y=-2根号下﹙根号下2x＋½根号下y﹚分之一=1/[√﹙√2＋½√2﹚]=1/[√﹙3√2/2﹚]=√[2/(3√2)]=√(√2/3)
