幾道數(shù)列的題目
1.等差數(shù)列an共有100項(xiàng),前10項(xiàng)和=265,后10項(xiàng)和=4765,則這100項(xiàng)的和S100=__
2.等差數(shù)列an中,a1=1,S10=100,如果數(shù)列bn滿足an=log2 bn,則b1+b2+b3+b4+b5=__
3.數(shù)列an中,a1=8,a4=2且滿足a(n+2)=2a(n+1)-an,n屬于自然數(shù)(1)求數(shù)列an通項(xiàng)(2)設(shè)Sn=|a1|+|a2|+...+|an| 求Sn (括號(hào)中為下標(biāo))
4.設(shè)無窮數(shù)列an的前n項(xiàng)和為Sn,已知a1=2,且當(dāng)n屬于自然數(shù)時(shí),總有4S(n+1)=3Sn+1 (1)求數(shù)列an的前n項(xiàng)和Sn的表達(dá)式 (2)求數(shù)列an的通項(xiàng)公式
5.已知數(shù)列an中,Sn是它的前n項(xiàng)和,并且S(n+1)=4an+2,a1=1 (1)設(shè)bn=a(n+1)-2an,求證數(shù)列bn是等比數(shù)列,并寫出其通項(xiàng)公式 (2)設(shè)cn=an/2^n,求證數(shù)列cn是等差數(shù)列