圆4x^2+4y^2-12x+16y+9=0的周长是

问题描述:

圆4x^2+4y^2-12x+16y+9=0的周长是

4x^2+4y^2-12x+16y+9=0
x^2+y^2-3x+4y+9/4=0
x^2-3x+9/4+y^2+4y+4-4=0
(x-3/2)^2+(y+2)^2=2^2
圆心坐标是(3/2,-2),半径是2.
所以周长=2πr=4π