若x^2+y^2=100,xy=-22,试确定x-y的值
问题描述：
若x^2+y^2=100,xy=-22,试确定x-y的值
答
x^2+y^2=100,xy=-22,
x²+y² -2xy = 100 +44 = 144
(x-y)²=144
x-y = ± 12