学年

質問の種類

数学 高校生

赤枠の部分でΣでn-1だからk-1に代入してn-2になると思ったんですがなんで3^n-1になるのか分かりません。

anil=pan+(nの1次式) 型の漸化式 基本例 117 (1)=1, an+1=3an+An によって定められる数列{an}の一般項を求めよ。 解答 an+1=3an+4n 指針 p.560 基本例題116の漸化式 pan+qのが定数ではなく、nの1次式となってい る。 このような場合は、 n を消去するために 階差数列の利用を考える。 CHART 漸化式 ampan+ (n の1次式) 階差数列の利用 ******. an+2=3an+1+4(n+1) n≧2のとき ②① から anti-ambm とおくと bn+1=36n+4 これを変形すると bn+1+2=3(6+2) ① とすると an+2an+1=3(an+1-a²) +4 また b1+2=a2-a+2=7-1+2=8 よって,数列{bm+2} は初項 8,公比3の等比数列で bm+2=8.3" なわち、14m=8.3"-1-2 連 an=a₁+(8.3k-¹-2)=1+ =4.3" -2n-1 n=1のとき 4・3°-2・1-1=1 α=1であるから, ③はn=1のときも成り立つ。 したがって an=4.3" -2n-1 別アプ ローチ 7-1 [R-1 ...... (3) 8(3-1-1) 3-1 検討 {an-(an+β)} を等比数列とする解法 (*) --2(n-1) ①00① 4/230 1/300 基本116 an+1=3an+4nが, an+1f (n+1)=3{an-f(n)} βの値を定める。 ①から an+1-{a(n+1)+B}=3{an-(an+B)} ゆえに an+1=3an-2an+α-2β これと an+1=3an+4n の右辺の係数を比較して よって [参考] (*)を導いた後, an+1- an=8.3”-1-2 に ① を代入して 4 を求めてもよい。 834-1)-2n ①のnにn+1 を代入する と②になる。 差を作り, n を消去する。 <{bn}は{an}の階差数列。 a=3a+47²5 a= 2 <az=341+4・1=7 -563- -an-army Kn≧2のとき n-1 an=a₁ + Σbk k=1 ① 初項は特別扱い 例題は an+1=pan+(nの1次式) の形をしている。 そこで, f(n)=an+βとおき, ・①の形に変形できるように α, -2a=4, a-28=0 3章 15 新 化式と数列 α=-2, β=-1 ゆえに f(n)=-2n-1 ①より,数列{an-(-2n-1)} は初項a,+2+1=4,公比3の等比数列であるから an-(-2n-1)=4.3"-1 したがって an=4.3" 1-2n-1 一般頂を求めよ。

解決済み 回答数: 1
英語 中学生

1945年の4月1日に始まった沖縄戦の間アメリカ軍の島への上陸があり, 80人以上の沖縄の人々が洞窟 に避難したあとその中で自殺したと考えられています。 がこの一文の訳なのですが、believedは何に訳されているのでしょうか??

t forced to commit suicide in the closing days of World War II, police have said. The boys, between the ages of 16 and 19, have said that they destroyed two *signboards and origami paper cranes left by visitors to the Chibichirigama cave between Sept. 5 and last Tuesday, police said Friday. 着 During the *Battle of Okinawa, which started on April 1, 1945, with the landing of the U.S. *army on the island, more than 80 Okinawa people were believed to commit suicide in the cave after taking *refuge there. Similar cases of suicide took place at other places during the battle. Family members of those people who killed themselves at the site during the war discovered the damage last Tuesday and reported it to police. Norio Yonaha, 63, who lost five members of his family in the suicide, told reporters that this was “an *insult to the people who died" there. Bottles and vases left behind by the dead people were also damaged. About 100,000 people, or almost a quarter of the local people, died in the three-month ground battle in Okinawa between the Japanese army and the U.S. army. In total, more than 200,000 (life) were lost, *including those of Americans. (2017, September 16). Japan Times Can you see “Chibichirigama” in the news report? “Gama” means “cave” in Okinawa. We can see natural gama here and there in Okinawa. Himeyurinotou is built on top of one of these gama. During World War II, gama were used as *trenches by the Japanese army and as places of refuge by Okinawa people. [ 7 ] because they had nothing to eat and no medicine for *wounds and sickness. Many were killed by the U.S. army who burned people to death. [ ] because they spoke Okinawa words. Some babies were also killed because they (cry). Many had to commit suicide because the Japanese army ordered then didn't stop to do so. [], but not always. In fact, there were lots of people who died in gama. Gama te us how terrible war is. NAZ

解決済み 回答数: 1