x^4-3x²y²+2y^4=(x²-2y²)(x²-y²)=(x-√2y)(x+√2y)(x-y)(x+y)
x^4-3x²y²+2y^4用十字相乘法:x^2 -y^2 \ / /\x^2 / \ -2y^2得:x⁴-3x²y²+2y⁴=(x²-y²)(x²-2y²)=(x+y)(x-y)(x+√2y)(x-√2y)
原式=(x²-y²)(x²-2y²)=(x+y)(x-y)(x+√2y)(x-√2y)