设公差为d,
a5=a1+4d ----(1)
a2=a1+d ----(2)
(1)-(2)得:a5-a2=3d=-6
即d=-2,将d代入(2)得:1=a1+(-2)
即a1=3
由等差数列的通项公式知:an=a1+(n-1)d=3+(n-1)(-2)=-2n+5
设公差为d,
a5=a1+4d ----(1)
a2=a1+d ----(2)
(1)-(2)得:a5-a2=3d=-6
即d=-2,将d代入(2)得:1=a1+(-2)
即a1=3
由等差数列的通项公式知:an=a1+(n-1)d=3+(n-1)(-2)=-2n+5