1）
方程只有一个实根
△=4(k+1)^2+4(1-2k)*1/2k=10k+4=0
k=-2/5
方程为：9x^2/5-6x/5+1/5=0
(3x-1)^2/5=0
x=1/3
2)
x1+x2=2(k+1)/(1-2k)
x1x2=-k/2(1-2k)
1/x1+1/x2=(x1+x2)/x1x2
=2(k+1)/(-k/2)
=-4(k+1)/k
=-6
6k=4k+4
k=2