（y-3）²=9（y+2）²

（y-3）²=9（y+2）²
（y-3）²=9（y+2）²

（y-3）²=9（y+2）²
[3(y+2)]²-(y-3)²=0
[3(y+2)+(y-3)][3(y+2)-(y-3)]=0
(4y+3)(2y+9)=0
y=-3/4,y=-9/2

（y-3）²=9（y+2）²
(1)（y-3）=3（y+2）
y=-4.5
(2)（y-3）=-3（y+2）
y=-0.75

（y-3）²=9（y+2）²
9（y+2）²-（y-3）²
=(3y+6)^2-(y-3)^2
=(3y+6+y-3)(3y+6-y+3)
=(4y+3)(2y+9)=0
y=-3/4,-9/2

(y-3)²=(3y+6)²
(y-3)²-(3y+6)²=0
(y-3+3y+6)(y-3-3y-6)=0
(4y+3)(-2y-9)=0
y = -0.75，或者，y = -4.5