Question

已知A=3X平方Y-4XY平方,B=-X平方Y-2XY平方,且A+B+C=0,求多项式C.

Answer 1

A=3x^2y-4xy^2

B=-x^2y-2xy^2

A+B=3x^2y-4xy^2-x^2y-2xy^2=2x^2y-6xy^2

A+B+C=0

C=-(A+B)=-(2x^2y-6xy^2)=6xy^2-2x^2y