k不等于0
(1)Δ=(k+2)^2-4*k*k/4
=4k+4>0
k>-1但k不等于0
(2)x1+x2=-(k+2)/k,x1x2=1/4
1/x1+1/x2=(x1+x2)/x1x2=-4(k+2)/k=0
k=-2