x^2+y^2=1,是单位圆,|x|=|y|=1,
1),-1≤x+y≤1,
2),1≤﹙y+2﹚/﹙x+1﹚=1+1/﹙x+1﹚≤3,x≠-1.y=0,x=1时代入原式=1.
3),﹙x+2﹚²+﹙y-3﹚²是(x^2+y^2=1)平移至(-2,3),的圆,.
x^2+y^2=1,是单位圆,|x|=|y|=1,
1),-1≤x+y≤1,
2),1≤﹙y+2﹚/﹙x+1﹚=1+1/﹙x+1﹚≤3,x≠-1.y=0,x=1时代入原式=1.
3),﹙x+2﹚²+﹙y-3﹚²是(x^2+y^2=1)平移至(-2,3),的圆,.