x1+x2=(k+1)/2
x1*x2=(k+3)/2
|x1-x2|=1
所以(x1-x2)^2=1
(x1-x2)^2=(x1+x2)^2-4x1*x2
=(k+1)^2/4-2(k+3)=1
k^2+2k+1-8k-24=4
k^2-6k-27=0
(k-9)(k+3)=0
k=9,k=-3