x的五次方+3x的四次方y-5x的三次方y的二次方-15x的平方y的三次方+4xy的四次方+12y的五次方
=x^5+3x^4y-5x^3y^2-15x^2y^3+4xy^4+12y^5
=x^4(x+3y)-5x^2y^2(x+3y)+4y^4(x+3y)
=(x+3y)(x^4-5x^2y^2+4y^4)
=(x+3y)(x²-y²)(x²-4y²)
=(x+3y)(x-y)(x+y)(x-2y)(x+2y)
=(x+y)(x+2y)(x+3y)(x-y)(x-2y)
∴值不可为33
∵x=y时
原式的值等于0