答：
1.(x-3)^2=0,解得x=3
2.(x+2)^2-(2x+1)^2=0
即(x+2+2x+1)(x+2-2x-1)=(3x+3)(-x+1)=0
解得x1=-1,x2=1
3.(2x+x+1)(2x-x-1)=(3x+1)(x-1)=0
解得x1=-1/3,x2=1