（2a+b)(2a-b)-(a-b)^2
=4a²-b²-a²+2ab-b²
=3a²+2ab-2b²
分解因式a^2-1+b^2-2ab=
=(a²-2ab+b²)-1
=(a-b)²-1
=(a-b+1)(a-b-1)
计算（2a+b)(2a-b)-(a-b)^2= 分解因式a^2-1+b^2-2ab=
（2a+b)(2a-b)-(a-b)^2
=4a²-b²-a²+2ab-b²
=3a²+2ab-2b²
分解因式a^2-1+b^2-2ab=
=(a²-2ab+b²)-1
=(a-b)²-1
=(a-b+1)(a-b-1)