∵b²-4ac=﹙k-2﹚²-8k≥0
﹙k-6﹚²≥32
∴ k≥6+4√2
或:k≤6-4√2
∵ a+b=k-2>0
∴ k>2
∵当x=1时,1-k+2+2k=0,k=﹣3<2
∴ a=b
∴ k=6+4√2.