=(x*2-4x)(x*2-4x+4)+4-1=(x*2-4x)+4(x*2-4x)+4-1=(x*2-4x+2)*2-1=(x*2-4x+1)(x*2-4x+3)=(x*2-4x+1)(x-3)(x+1)
问老师
诶~~~~~~~~~~~~~