已知x-y=3,xy=2,求下列代数式的值(1)(x-2)(y+2)(2)x^3y-2x²y²+xy^3

问题描述:

已知x-y=3,xy=2,求下列代数式的值
(1)(x-2)(y+2)
(2)x^3y-2x²y²+xy^3

(1)(x-2)(y+2)
=xy+2x-2y-4
=xy+2(x-y)-4
=2+2×3-4
=4
(2)x^3y-2x²y²+xy^3
=xy(x²-2xy+y²)
=xy(x-y)²
=2×3²
=18

x-y=3,xy=2
(1)(x-2)(y+2)
=xy+2(x-y)-4
=2+2×3-4
=4
(2)x^3y-2x²y²+xy^3
=xy(x²-2xy+y²)
=xy(x-y)²
=2×3²
=18