4(3x-y)^2-(x+3y)^2
=[2(3x-y)-(x+3y)][2(3x-y)+(x+3y)]
=(5x-5y)(7x+y)
4(3x-y)^2-(x+3y)^2
=[2(3x-y)+(x+3y)][2(3x-y)-(x+3y)]
=(7x+y)(5x-5y)
=5(7x+y)(x-y)
4(3x-y)^2-(x+3y)^2
=[2(3x-y+x+3y)][2(3x-y)-x-3y]
=4(4x+2y)(2x-4y)
=16(2x+y)(x-2y)
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