x^2-ax+4=0(a
问题描述：
x^2-ax+4=0(a
错了，题目是求√(x1\x2)+√(x2\x1)
答
由根与系数的关系,得：
x₁+x₂=a
x₁*x₂=4
则有：
[√(x₁/x₂)+√(x₂/x₁)]²
=(x₁/x₂)+(x₂/x₁)+2
=(x₁²+x₂²)/(x₁*x₂)+2
=(x₁²+x₂²+2x₁*x₂-2x₁*x₂)/4+2
=[(x₁+x₂)²-2x₁*x₂]/4+2
=[a²-8]/4+2
=a²/4
由于a