(1)应该是x^2-4xy+4y^2-9吧?
=(x-2y)²-3²
=(x-2y+3)(x-2y-3)
(2)(a+b)^2+4(a-b)^2-4(a^2-b^2)
=(a+b)²-2×2(a-b)(a+b)+[2(a-b)]²
=[(a+b)-2(a-b)]²
=(3b-a)²
不懂的还可以问!满意请及时采纳! O(∩_∩)O
解析,
(1)x²-4xy+(2y)²-9
=(x-2y)²-3²
=(x-2y-3)(x-2y+3)
(2)(a+b)²+4(a-b)²-4(a²-b²)
=(a+b)²-2*2(a-b)*(a+b)+[2(a-b)]²
=[(a+b)-2(a-b)]²
=(3b-a)²
(x-2y+3)(x-2y-3) (3b-a)²