易得,(k+2)x=5
x=5/(k+2)
因方程的解为自然数,易得x可取1,-1,5,-5
x=1时,可得k=3
x=-1时,可得k=-7
x=5时,可得k=-1
x=-5时,可得k=-3
综上,可得k的值为-7,-3,-1,3