已知：a²+b²=2,a+b=1,求ab和a-b的值
问题描述：
已知：a²+b²=2,a+b=1,求ab和a-b的值
答
(a+b)²=a²+b²+2ab
1=2+2ab
2ab=-1
ab=-1/2
(a-b)²
=a²+b²-2ab
=2-2×(-1/2)
=2+1
=3
a-b=±根号3