упростите вырожение (3x-y)(9x^2+y^2)(3x+y)-81x^4

(3x-y)(3x+y)(9x^2+y^2)-81x^4(9x^2+3xy-3xy-y^2)(9x^2+y^2)-81x^4(9x^2-y^2)(9x^2+y^2)-81x^481x^4+9x^2y^2-9x^2y^2-y^4-81x^4-y^4

(3x-y)(9x²+y²)(3x+y)-81x⁴==[(3x-y)(3x+y)](9x²+y²)-81x⁴==(9x²-y²)(9x²+y²)-81x⁴==81x⁴-y⁴-81x⁴=-y⁴