若(x+y)^2=7,(x-y)^2=3,则xy的值为
问题描述：
若(x+y)^2=7,(x-y)^2=3,则xy的值为
答
(x+y)^2=7
x²+2xy+y²=7.①
(x-y)^2=3
x²-2xy+y²=3.②
①-②
4xy=4
xy=1
不懂再问哦