解:4(x+y+z)^2-9(x-y-z)^2
=[2(x+y+z)]^2-[3(x-y-z)]^2
=[2(x+y+z)+3(x-y-z)][2(x+y+z)-3(x-y-z)]
=(2x+2y+2z+3x-3y-3z)(2x+2y+2z-3x+3y+3z)
=(5x-y-z)(-x+5y+5z)
=-(5x-y-z)(x-5y-5z)
=(2x+2y+2z+3x-3y-3z)(2x+2y+2z-3x+3y+3z)
=(5x-y-z)(-x+5y+5z)
=-(5x-y-z)(x-5y-5z)
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