已知等差数列{an}的公差与等比数列{bn}的公比相等,且都等于d(d>0,且d≠1),又知a1=已知等差数列{an}的公差与等比数列{bn}的公比相等,且都等于d(d>0,且d≠1),又知a1=b1,a3=3b3,a5=5b5,求an,bna3=a1+2

来源:学生作业帮助网 编辑:作业帮 时间:2024/11/25 10:12:32
已知等差数列{an}的公差与等比数列{bn}的公比相等,且都等于d(d>0,且d≠1),又知a1=已知等差数列{an}的公差与等比数列{bn}的公比相等,且都等于d(d>0,且d≠1),又知a1=b1,a3=3b3,a5=5b5,求an,bna3=a1+2
xRMo@+VPQLuQ6& ! *(4@s?AN )z̛j|NQwpG4w2/8#h1D/}53AķK.tgf>e| xW 燽%#`ԣǻ,4x(ʷz tlB[('PvFlX*:.TtNFlO>wgo^GO^UQVR#aX>yECS8J&$5`Z-%HtU?HUi~!S `-'g*;"Hj" U$ #)XB!B:)( aCPd>G G~-ֲ/[U MͿm/׸r_<}/WtZgViK5B7 F}wLs:&j76CAJyR-' A/K"nsH[H fU,_Ҳh&8Y\M`aĴ_jpַ 

已知等差数列{an}的公差与等比数列{bn}的公比相等,且都等于d(d>0,且d≠1),又知a1=已知等差数列{an}的公差与等比数列{bn}的公比相等,且都等于d(d>0,且d≠1),又知a1=b1,a3=3b3,a5=5b5,求an,bna3=a1+2
已知等差数列{an}的公差与等比数列{bn}的公比相等,且都等于d(d>0,且d≠1),又知a1=
已知等差数列{an}的公差与等比数列{bn}的公比相等,且都等于d(d>0,且d≠1),又知a1=b1,a3=3b3,a5=5b5,求an,bn
a3=a1+2d a5=a1+4d
b3=b1*d^2 b5=b1*d^4
a1+2d=b1*d^2 a1+4d=5b1*d^4
接下来该怎么解呢

已知等差数列{an}的公差与等比数列{bn}的公比相等,且都等于d(d>0,且d≠1),又知a1=已知等差数列{an}的公差与等比数列{bn}的公比相等,且都等于d(d>0,且d≠1),又知a1=b1,a3=3b3,a5=5b5,求an,bna3=a1+2
a3=3b3
a1+2d=3a1d²
(3d²-1)a1=2d
a1=2d/(3d² -1)
a5=5b5
a1+4d=5a1d⁴
(5d⁴-1)a1=4d
a1=4d/(5d⁴-1)
2d/(3d²-1)=4d/(5d⁴-1)
5d⁴-6d²+1=0
(d-1)(5d-1)=0
d=1(d≠1,舍去)或d=1/5
a1=2d/(3d² -1)=2/(3d -1/d)=2/(3/5 -5)=-5/11
an=a1+(n-1)d=-5/11 +(1/5)(n-1)=-36/55 +n/5
bn=b1d^(n-1)=(-5/11)×(1/5)^(n-1)=-1/[11×5^(n-2)]

已知等差数列{an}的公差为b,等比数列{bn}的公差为a,且a1=b1=a,a...已知等差数列{an}的公差为b,等比数列{bn}的公差为a,且a1=b1=a,a2=b2,a1,a2,a4,成等比.求数列{an}{bn}的通项公式 已知等差数列{an}的公差d不等于0且a1,a3,a9成等比数列,则看图 已知等差数列{an}的公差为2,若a1,a3,a4称等比数列,则a2= 已知等差数列{an}的公差为3,若a1,a3,a4成等比数列,则a2= 已知等差数列{an}的公差为3 若a2 a4 a8成等比数列 则a4等于 已知等差数列an的公差为-2,且a2,a4,a5成等比数列,则a2等于 已知等差数列[an]的公差d不等于零,若a5,a9,a15成等比数列,公比为? 已知等差数列an的公差不为零,a5,a9,a15,成等比数列,公比? 已知数列{lgan}是首项为3,公差为2的等差数列,求证:{an}是等比数列. 已知等差数列{an}的公差和等比数列{bn}的公比都是d,又知d≠1,且a4=b4,a10=b10:(1)求a1与d的值; (2)b(2)b16是不是{an}中的项? 等比数列和等差数列的题目1.等比数列{An}的各项都为正数,且A2*A8=16,求logA1+logA2+logA3……+logA9的值2.已知等差数列{An}的公差与等比数列{Bn}的公比相等,且都等于d(d>0).若A1=B1,A3=3B3,A5=5B 已知等差数列{an}的公差d≠0,且a1,a3,a9是某等比数列的前三项,求等比数列公比 已知等差数列{an}的首相为a,公差为b,等比数列{bn}的首相为b.已知等差数列{an}的首相为a,公差为b,等比数列{bn}的首相为b,公差为a,其中a,b都是大于1的正整数,且a1 已知等差数列{An}的公差d 已知等差数列{an}的公差d 已知等差数列{an}的公差d 已知公差不为0的等差数列an与等比数列bn,a1=bi,a3=b3,a7=b5如题,A)b11=a13,B) b11=a31,C) b11=a63,D) b63=a11 已知等差数列{an}的公差d不等于0,数列{bn}是等比数列,a1=b1=1,a2=b2,a4=b4已知等差数列{an}的公差d不等于0,数列{bn}是等比数列,a1=b1=1,a2=b2,a4=b41,求出数列{an}与{bn}的通项公式2,设cn=an*bn,求