Đáp án:
[18.$(x-y)^{3}$ +6.$(y-x)^{4}$ -15. $(x-y)^{3}$ +$(y-x)^{2}$ ]:$(x-y)^{2}$
=[18.$(x-y)^{3}$ +6.$(x-y)^{4}$ -15. $(x-y)^{3}$ +$(x-y)^{2}$ ]:$(x-y)^{2}$
=$(x-y)^{2}$ [18(x-y)+6$(x-y)^{2}$ -15.(x-y)+1]:$(x-y)^{2}$
=18(x-y)-15(x-y)+6$(x-y)^{2}$ +1
=6$(x-y)^{2}$ +3(x-y)+1