巡夜人
幼苗
共回答了13个问题采纳率:92.3% 举报
解
x1,x2是方程的两根
由韦达定理
x1+x2=-2
x1x2=1/2
∴
(1)1/x1+1/x2
=(x1+x2)/(x1x2)
=(-2)/(1/2)
=-4
(2)(x1-x2)²
=(x1+x2)²-4x1x2
=(-2)²-4×1/2
=4-2
=2
(3)x1²+x2²-3x1x2
=(x1+x2)²-5x1x2
=(-2)²-5×(1/2)
=4-5/2
=3/2
(4)x1²x2+x2²x1
=x1x2(x1+x2)
=1/2(-2)
=-1
1年前
5