x²+y²+2x-2y+1=0x²+2x+1+y²-2y+1=1(x+1)²+(y-1)²=1令x=-1+sina y=1+cosa2y-2x-1=2+2cosa+2-2sina-1=2(cosa-sina)+3=2√2cos(a+π/4)+3当cos(a+π/4)=-1时,2y-2x-1有最小值(2y-2x-1)mi...