(2x-3y)²-(y+3x)(3x-y) (a-2b+3)(a+2b-3) [(x-y)²+(x+y)²](x²-y²)

(2x-3y)²-(y+3x)(3x-y) (a-2b+3)(a+2b-3) [(x-y)²+(x+y)²](x²-y²)
(2x-3y)²-(y+3x)(3x-y) (a-2b+3)(a+2b-3) [(x-y)²+(x+y)²](x²-y²)

(2x-3y)²-(y+3x)(3x-y) (a-2b+3)(a+2b-3) [(x-y)²+(x+y)²](x²-y²)
(2x-3y)²-(y+3x)(3x-y)
=4x^2-12xy+9y^2-9x^2+y^2
= -5x^2-12xy+10y^2
(a-2b+3)(a+2b-3)
= a^2-(2b-3)^2
=a^2-4b^2+12b-9
[(x-y)²+(x+y)²](x²-y²)
=(x^2-2xy+y^2+x^2+2xy+y^2)(x^2-y^2)
=2(x^2+y^2)(x^2-y^2)
=2x^4-2y^4

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