x+y=m xy=n,求(x-y)²和x²+y²

问题描述:

x+y=m xy=n,求(x-y)²和x²+y²

解: x+y=m xy=n
(x-y)²
=(x+y)²-4xy
=m²-4n
x²+y²
=(x+y)²-2xy
=m²-2n
祝你开心