Question

已知x+y=2,xy=-1,求x3次方y+2x平方y平方+xy3次方的值

Answer 1

x³y+2x²y²+xy³
=xy（x²+2xy+y²）
=xy（x+y）²
=-1*2²
=-4

Answer 2

x^3y+2x^2y^2+xy^3
=xy(x^2+2xy+y^2)
=xy(x+y)^2
=(-1)*2^2
=-4