x²+2x+y²-4y+5=0(x²+2x+1)+(y²-4y+4)=0(x+1)²+(y-2)²=0(x+1)²≥0(y-2)²≥0而：(x+1)²+(y-2)²=0(x+1)²=0(y-2)²=0∴x=-1 y=2y^x=2^(-1)=½