Question

3x的立方-3x的平方-y的平方+5y+x的平方-5y+y的平方

Answer 1

3x^3-3x^2-y^2+5y+x^2-5y+y^2

=3x^3+(-3x^2+x^2)+(-y^2+y^2)+(5y-5y)

=3x^3+(-3+1)x^2+(-1+1)y^2+(5-5)y

=3x^3-2x^2