(9x^2+4y^2)(3y+3y)(3x-2y)

问题描述:

(9x^2+4y^2)(3y+3y)(3x-2y)

(9x^2+4y^2)(3x+2y)(3x-2y)
=(9x^2+4y^2)(9x^2-4y^2)
=81x^4-16y^4