(2x-1)²-(x+2)²=0
[(2x-1)+(x+2)][(2x-1)-(x+2)]=0
(3x+1)(x-3)=0
x=1/3,x=3
原式=(m²-2m)²+2(m²-2m)+1
=(m²-2m+1)²
=(m-1)^4