to nghi bai nay con co cach don gian hon :
(a-x)y^3 - (a-x+x-y)x^3+(x-y)a^3
=(a-x)y^3 - (a-x)x^3 - (x-y)x^3 + (x-y)a^3
=(a-x)(y^3-x^3) - (x-y)(x^3-a^3)
=(a-x)(y-x)(y^2+x^2+xy) - (y-x)(a-x)(x^2+a^2+xa)
=(a-x)(y-x)(y^2+xy-a^2-xa)
=(a-x)(y-x)((y-a)(y+a)+x(y-a))
=(a-x)(y-x)(y-a)(y+a+x)
the nao , loi giai cua to cung dc chu?, mong cac ban gop y!