数列{an}是等差数列,a1=1,an=-512,Sn=-1022求公差d
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![数列{an}是等差数列,a1=1,an=-512,Sn=-1022求公差d](/uploads/image/z/2695410-18-0.jpg?t=%E6%95%B0%E5%88%97%EF%BD%9Ban%EF%BD%9D%E6%98%AF%E7%AD%89%E5%B7%AE%E6%95%B0%E5%88%97%2Ca1%3D1%2Can%3D-512%2CSn%3D-1022%E6%B1%82%E5%85%AC%E5%B7%AEd)
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数列{an}是等差数列,a1=1,an=-512,Sn=-1022求公差d
数列{an}是等差数列,a1=1,an=-512,Sn=-1022求公差d
数列{an}是等差数列,a1=1,an=-512,Sn=-1022求公差d
an=a1+(n-1)d
Sn=(a1+an)n/2
-171
Sn=(a1+a2)n/2 , an=a1+(n-1)d 就可以求出来了
先由Sn=n*(an+a1)/2中求出n: n=4
再由an=a1+(n-1)d求出d: d=-171
n=4,d=-171