若x-y=5.xy=6,x^2y+xy^2等于多少
问题描述：
若x-y=5.xy=6,x^2y+xy^2等于多少
11点之前有奖赏
答
(x+y)²
=x²+2xy+y²
=(x²-2xy+y²)+4xy
=(x-y)²+4xy
=49
所以x+y=±7
x²y+xy²
=xy(x+y)
=±42