a^2+2(2b-c)a-12b^2+20bc-8c^2x^2(9-y^2)+(y^2-1)+8xya^3-6a^2b+12b^2-9b^3

问题描述:

a^2+2(2b-c)a-12b^2+20bc-8c^2
x^2(9-y^2)+(y^2-1)+8xy
a^3-6a^2b+12b^2-9b^3