因式分解：(x+y)²+4(x-y)²-4(x²-y²)

因式分解：(x+y)²+4(x-y)²-4(x²-y²)
因式分解：(x+y)²+4(x-y)²-4(x²-y²)

因式分解：(x+y)²+4(x-y)²-4(x²-y²)
(x+y)²+4(x-y)²-4(x²-y²)
=(x+y)²-2×(x+y)(x-y)+[2(x-y)]²
=[(x+y)-2(x-y)]²
=(x+y-2x+2y)²
=(x-3y)²

(x+y)²+4(x-y)²-4(x²-y²)
=x²+y²+2xy +4x²+4y²-8xy -4x²+4y²
=x²+9y²-6xy
=(x-3y)²