已知x2+y2-4x-6y+12=0,则x+2y的取值范围是

已知x2+y2-4x-6y+12=0,则x+2y的取值范围是
已知x2+y2-4x-6y+12=0,则x+2y的取值范围是

已知x2+y2-4x-6y+12=0,则x+2y的取值范围是
x²+y²-4x-6y+12=0则
（x-2)²+(y-3)²=1
设x-2=cosa,y-3=sina ,a∈(0,2π],则
x+2y
=cosa+sina+5
=√2sin(a+π/4)+5
=>5-√2≤x+2y≤5+√2