a(n+1)-a n=3 * 2的n-1次方 求an通项打错了、、是a(n+1)-2a n=3 * 2的n-1次方 求an通项 a1=1

a(n+1)-a n=3 * 2的n-1次方 求an通项打错了、、是a(n+1)-2a n=3 * 2的n-1次方 求an通项 a1=1
a(n+1)-a n=3 * 2的n-1次方 求an通项
打错了、、是a(n+1)-2a n=3 * 2的n-1次方 求an通项 a1=1

a(n+1)-a n=3 * 2的n-1次方 求an通项打错了、、是a(n+1)-2a n=3 * 2的n-1次方 求an通项 a1=1
a(n+1)-a(n)=3 * 2^(n-1)
a(n)-a(n-1)=3 * 2^(n-2)
a(n-1)-a(n-1)=3 * 2^(n-3)
.
a2-a1=3 * 2^0=3
叠加得：a(n)-a1=3*2^(n-2)+3*2^(n-3)+,+3=3[1-2^(n-1)]/(1-2)=3[2^(n-1)-1]
所以a(n)=3[2^(n-1)-1]+a1
题目是不是却了一个条件?

………………………………
你好像没给首项
用累加发和分组求和
结果是An=3×2^n-3-A1

time soon Chiru train a new one-stop, like the scenery out the window, like, 2008 so hurry across from our sight. Looking back on the harvest and regret are graceful, fast or even faster finish. In th...

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time soon Chiru train a new one-stop, like the scenery out the window, like, 2008 so hurry across from our sight. Looking back on the harvest and regret are graceful, fast or even faster finish. In the end is the time to be flung behind us,Maccosmetics, all the frustration and loss can start again; or the old time push us, hopes and dreams they have lost an opportunity. Another year has come short spring, but also the reincarnation of the end and beginning, do not forget the 08 in this special year, because there you my story.
do not remember is the day to convey to you my heart, the impression that we started to chat or play? I do not joke, the opposite of you have already blush. From that, you will not ask me why like you, because you think you can give me the power. You wrote my essay, bit by bit. A person, I will often open to see, savor each time you feel like it is a wonderful aftertaste, like look at old photos or old movies As their minds were free to
time together, we feel the silence each other, care about each other, happy with each other's happiness, sadness with each other's sorrow, as one pair of passers-by, it seems there is no expression in others, but also like a Confucian to the phase Mo's husband, a look sufficient to understand all the other side. Sometimes we play fun, I like to haunt you let me go look; every day at noon I like to quietly stand beside you and enjoy your hair; standing at the window every afternoon I watched you leave, And you will be pleased to my call; seat every night we will wait quietly in the mobile phone next to each other. Sometimes we even like a child, the other one do not intend for the words of anger, like a child, after a while and He Hao a; sometimes like a parent, care for the warmth of each other; sometimes like long lost friends, the phone always so much to say; sometimes as competitors,Mac make up, deliberately gas with each other, but is in fact abused themselves, because we are very concerned about each other's feelings. Often complain about your stupid, even the most basic things that a girlfriend will not do. Too much ~ ~ too much.
08 年 to have kind of a day in the past. Time will never care about it walking speed, because it some time, and we, as a form of life in all things, you can not numb, let us cherish and be kind to the fate it: see it as something precious, because it comes from Naturally, there is no secular processing and loaded with; goods such as tea it, quietly feel it bitter fragrance,wholesale mac makeup, it will make people soul-stirring; love it, such as life, because it'll be our life.
gradually when the firecrackers sounded in 2009, whether declared the end of the old or new beginning, remember that in 2008 the story of me and you.

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