(x-3)^2+(y-2)^2=1 2跟正确答案不一样啊······1切线y=kxx^2+y^2-6x-4y+12=0(1+k^2)x^2-(6+4k)x+12=0判别式(6+4k)^2-4(1+k^2)*12=08(k-3/4)^2=3/2 k=3±√3/4k=y/xx/y=1/kx/y最大=4/(3-√3)=2(3+√3)/3=2+2√3/3最小=4/(3+√3)=2(3-√3)/3=2-2√3/32x^2+y^2最大=(3+3/√13)^2+(2+2/√13)^2=13*(1+1/√13)^2=(√13+1)^2=14+2√13最小=（3-3/√13)^2+(2-2/√13)^2=13*(1-1/√13)^2=(√13-1)^2=14-2√133x+y=5+cosa+sina =5+√2cos(a+45)a=45, x+y最大=5+√2a=135 最小=5-√2