已知等差数列{an}满足a1=2,an=an+1-2,求an,及S10

问题描述:

已知等差数列{an}满足a1=2,an=an+1-2,求an,及S10

∵an=an+1-2
∴an+1-an=2
即d=2
∴an=a1+(n-1)d=2+(n-1)×2=2n
S10=10×2+[10×(10-1)]÷2×2=110