當(dāng)n=1時(shí)，a1=S1=-1．
當(dāng)n≥2時(shí)，an=Sn-Sn-1=-n2-[-（n-1）2]=1-2n，當(dāng)n=1時(shí)也成立．
∴d=-2．
故選C．
設(shè)等差數(shù)列{an}的公差是d，如果它的前n項(xiàng)和Sn=-n2，那么（ ?。?A.an=2n-1，d=-2 B.an=2n-1，d=2 C.an=-2n+1，d=-2 D.an=-2n+1，d=2
設(shè)等差數(shù)列{an}的公差是d，如果它的前n項(xiàng)和Sn=-n2，那么（ ?。?br/>A. an=2n-1，d=-2
B. an=2n-1，d=2
C. an=-2n+1，d=-2
D. an=-2n+1，d=2
B. an=2n-1，d=2
C. an=-2n+1，d=-2
D. an=-2n+1，d=2
數(shù)學(xué)人氣：709 ℃時(shí)間：2020-09-23 13:17:59
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