4a²+4a-4a²b+b+1=(2a+1)^2-b(2a+1)(2a-1)=(2a+1)(2a+1-2ab+b)
a（a²-a-1）+1=a^3-a^2-a+1=a^2(a-1)-(a-1)=(a-1)(a^2-1)=(a-1)^2(a+1)
ab（m²+n²）+mn（a²+b²）=am(bm+an)+bn(an+bm)=(am+bn)(an+bm)