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数学 高校生

この問題で なぜa<-7, 20<aの範囲を考えないのですか? また、なぜ3つの実数解をもつ時しか考えないのか分からないです

296 日前 1983次関数のグラフに引ける機械の本数 ○○する。 y=x-9x415x-7 に対して、軸上の点)から相異なる。 本の接線を引くことができるように,実数aの値の範囲を定めよ。 [日本歯大 ] CHARTO 解答 246 OLUTION 3次関数のグラフの接線 接点が異なると, 接線が異なる したがって (接点の個数)=(接線の本数) が成立する。 上の点(t, ピー9t+15t-7) における接線が点A(0, α) を通る→ 接線の方 程式に (0, α) を代入して g (t)=α の形にする 曲線 y=g(t) は固定し,直 線y=a を動かし, 曲線と直線の共有点について調べる。・・・・・・! y=x-9x2+15x-7 から y'=3x²-18x+15 曲線上の点(t, ピー9t2+15t-7)における接線の方程式は y-(1-9t2+15t-7)=(3t²-18t+15)(x-t) すなわちy=(3²-18t+15)x-2t3+9t2-7 この直線が点A(0, α)を通るとき -21³+91²-7=a ① 3次関数のグラフでは、 接点が異なると接線も異なる。 ゆえに,t の3次方程式 ① が異なる3つの実数解をもつとき, 点Aから曲線に3本の接線が引ける。 ここで,g(t)=-2t3+962-7 とすると g'(t)=-6f2+18t =-6t(t-3) g (t) の増減表は,次のようになる。 3 + 0 t g'(t) g(t) 0 0 |極小 -7 ...... 極大 20 y 20 0 3 y=g(t)| y=20 y=a J-7 基本 175, 194 よって, y=g(t) のグラフは右の図のようになる。 ① の異なる実数解の個数,すなわち y=g(t) のグラフと直線 y=aとの共有点の個数が3となるようなαの値の範囲は -7<a<20 別解 解答と5行目ま この直線が点A(0, 263-912+ 3次関数のグラフ ゆえに,tの3次 き,点Aから曲線 ここで, h(t)=2t h'(t)=6 h (t) の増減表は仁 y-f(t)=f'(r)(x-t) この断り書きは重要。 ◆g (t) = α の実数解の個数 ↓ y=g(t), y=a の共有 点の個数 ② の異なる実数 軸との共有点が なるときである よって 求める y=f(x) 上の接点の個数 ↓ y=f(x)に引ける接線 の本数 t h' (t) h(t) (INFORMATIC 前ページでも角 inf. y=f(x) に引ける接 線の本数は 720のとき2本 a<-720 <a のとき 1本である。 [証明 3次 と仮定する ナ は, x=α の形で等 ところが よって, 注意 4次 で接点 また、平 ようなと PRACTIC kは定

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英語 高校生

論評の問題です。 教えてほしいです。

Exercise 6 1 Use the words in the bracket and write present perfect sentences.(7)→AB 1) The president at the airport. [ just / arrive] 2) I 3) ad gult ed sivom 2 Fill in the blanks so that they mean almost the same thing. 1) a) Kenji came to New York two weeks ago, and he is still here. b) Kenji ( ) in New York for two weeks. ) ( burl 9/12 2) a) Mr. Williams went back to London, and he isn't here now. b) Mr. Williams ( 4 my room. your lunch yet? - No, not yet. ) ( ) back to London. 3) a) I came back from Hawaii yesterday. It was my second visit there. b) I ( ) to Hawaii twice. )( ) ( [ already / clean] [you / finish] does word bad sri 4) a) I'll climb Mt. Fuji tomorrow. This will be my first time to climb it. b) I ( od sivom ) ( ) ( ) Mt. Fuji before. 5) a) Ms. Sato became a music teacher five years ago, and she still teaches music. b) Ms. Sato ( ) ( ) a music teacher for five years. ) ( 3 Fill in the blanks to complete the sentences. 1) How long ( ) you ( antenge 2) John ( ) in Japan since he was twenty. (ずっと日本に住んでいる) 3) Jim ( ) ( 4) ( ) ( 5) The children ( ) ( ) ( STT D bad I yim bedefnit ovarl lliw i him? (いつからのお知り合いですか) B →B Choose the appropriate form of the verb and complete the sentences. 1) When (did you start / have you started) taking piano lessons? 2) My mother (never went / has never been ) abroad before. 3) We (discussed / have discussed) environmental issues at the meeting last week. 4) My sister (wanted / has wanted) that guitar for a long time, but it's expensive. 5) I (didn't receive / haven't received) a reply from her yet. s ) snow because he was born in Hawaii. (一度も見たことがない) ) ( ) an email in English? (あなたは今まで書いたことがありますか) all of the cookies. (もうすべて食べてしまった) ) ( →B Put it into English - Context writing - Ken:1)日本に住んでどれくらいになりますか。 Laura: 2) ここに住んで10年になります。 Ken: That's a long time. So 3) たこ焼きを食べたことはありますか。 Laura: Yes, of course. 4) 何度も食べたことがあります。 But 5) お好み焼きを食べたことは一度も ありません。

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英語 高校生

この文章について、下から2番目の「one thong is clear now」のone thingが示す内容は何なのですか?

New Media There have been many great inventions in history, for example, the wheel, paper, and the steam engine. Inventions can change people's lives. They can create new businesses and new culture. This is especially true for two recent inventions personal computers and the Internet. The Internet has become an important kind of media, an important means of communication for many people. This new media form is different from older forms, such as print media (books, newspapers, and magazines) and broadcast media (radio and television) in at least two ways. LF-4 First, people can get and send information easily on the Internet. They can access information at almost any time. People can use the Internet to communicate in many ways. It's easy to send pictures, videos, and messages, so people are sending and viewing a lot of them. However, this may also be a problem. People are spending too much time on their smartphones and computers. 3» A second difference is content. With other media, such as newspapers, magazines, TV, and radio, the content is usually made by a limited number of professionals. However, nowadays, almost anyone can create and upload content to the Internet. That means we can get much more information, but we have to be careful. We don't always know who made the content, and some of the LF-3 information may be incomplete or incorrect. 4" The Internet has become an important way to get and share information. We won't know the real effect of the differences between the Internet and other media for years. However, one thing is clear now. It has already become an essential part of our culture. 1» 2»

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