Question

已知x减y是1,x乘y是2,求x的3次方y减2x平方y平方加xy3次方

Answer 1

x-y=1

xy=2

x^3y-2x^2y^2+xy^3

=xy(x^2-2xy+y^2)

=xy(x-y)^2

=2×1^2

=2