c²-a²-2ab-b²
=c²-(a²+2ab+b²)
=c²-(a+b)²
=[c+(a+b)][c-(a+b)]
=(c+a+b)(c-a-b)
m的5次方-m
=m(m的4次方-1)
=m(m²+1)(m²-1)
=m(m²+1)(m+1)(m-1)
(x²+2x)²+2(x²+2x)+1
=[(x²+2x)+1]²
=(x²+2x+1)²
=[(x+1)²]²
=(x+1)的4次方