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英語 中学生

分からないので教えて下さい!!!

次の問いの答えとして最も適当なものを、①~①のうちから1つ選べ。 Why couldn't Mr. Black and the children go for a swim one day ? 1 Because they had to go to the lake and look into the water. Because Mr. Black couldn't swim well 読解 問1 読解 3 Jill, Ellen, Bob, and Edward lived near a lake. They could go for a swim every day. A man named Mr. Black lived near the lake, too, Sometimes Mr. Black went Because the lake got dirty with garbage, oil and tires. 3 Because they could not get a boat. One day they asked him to go for a swim with them. Mr. Black said, “We can't o a swim. We may never swwim in the lake again. “Why not ?" asked Edward. swimming with the children. 下線部(ア)について,何をするために彼らは出かけたのか,日本語で答えなさい。 問2 「Because the lake is polluted." said Mr. Black. “There's a new Sign at the lake. h says: No Swimming, Polluted." “What is polluting the lake ?" asked Jill. 明3 下線部(イ) peopleが指すものとして、本文中に書かれていないものを、次の0~ ののうちから1つ選べ。 タイヤを捨てた車の所有者 “Let's go down to the lake and look at it." said Mr. Black. (ア) Mr. Black and the children went to the lake on a sunny Sunday. They looked into the water. It wasn't clean. They walked around the lake and they saw why it wasn't の 2 汚水を流した工場の人々 O 湖の近くに住む人々 clean. 3 油を流したボートの所有者 “Look at that *garbage in the water,” said Jill. “That's what's polluting the lake,” Edward saw oil floating on the water. “That oil pollutes the water, too,” said Edward. “It comes from boats on the lake." 下線部(ウ)について, 人々は何がわかっていたのか、 日本語で答えなさい。 問4 “Come here, " said Ellen. “Take a look at this. There are tires in the lake !" “Why would people throw tires into a lake ?" asked Bob. “They just don't stop to think," said Mr. Black. “But they are not the only ones who pollute the lake. The people who run that factory pollute the water, too." Bob looked at Mr. Black. ““What can we do ? How can we stop the pollution ?” he asked. “Well, we must get help from other people. We can't do it alone,” said Mr. Black. Mr. Black had a firiend who worked for a newspaper company. He asked him to help. The next day, the story about the pollution was reported in the newspaper. Many people read about the story. They talked of the pollution. They talked of ways to clean it up. One day ( People met at the lake. They came to clean it up. They cleaned out the garbage. Then they cleaned out the tires. They set up big cans. Then they put signs on the cans. The signs read, “Put Your Garbage Here.” People who lived near the lake came to help. People who had boats came to help. And, people from the factory also came to help. (ウ) They knew that it would take a long time to get the lake clean again. But they did not give up. They all hoped that someday the “No Swimming" sign would come down and the people could swim in the lake again. 注) garbage=ごみ

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数学 高校生

合成関数の問題なのですが。まだ高1なので代入した時に何故2f(x)になるのかがわかりません。ちなみにこの問題の(2)です。よろしくお願いいたします。

a 5 OOOO0 重要 例題68 定義域によって式が異なる関数 (2) 関数 f(x)(0Sx<4) を右のように定義すると き,次の関数のグラフをかけ。 (1) y=f(x) 114 (0Sx<2) 18-2x (2<xミ4) 2x f(x)= (2) y=f(f(x)) 1 指針>定義域によって式が変わる関数では, 変わる 境目のx, yの値 に着目。 (2) f(f(x)) はf(x) の xにf(x)を代入した式で, 0Sf(x)<2 のとき 2f(x), (1)のグラフにおいて, 0<f(x)<2となるxの範囲と, 2<f(x)<4となるxの範囲を見 極めて場合分けをする。 2Sf(x)<4のとき 8-2f(x) 解答 変域ごとにグラフをかく。 4(1)のグラフから,f(x) の 変域は 0<x<1のとき 0Sf(x)<2 1Sx<3のとき 2<f(x)<4 (1) グラフは図 (1)。 |2f(x) (2) f(f(x))={ (0Sf(x)<2) 8-2f(x) (2<f(x)<4) よって,(1)のグラフから 0Sx<1のとき 1Sx<2のとき 2Sx<3のとき 3<x<4のとき よって,グラフは 図 (2)。 f(f(x))=2f(x)=2-2x=4x f(f(x))=8-2f(x)=8-2-2.x=8-4x f(f(x))=8-2f(x)=8-2(8-2x)=4x-8 f(f(x))=2f(x)=2(8-2x)=D16-4x 3<x<4のとき 0Sf(x)<2 また,1SxS3のとき, f(x)の式は 1Sx<2なら f(x)=D2x 2<x<3なら f(x)=8-2.x のように,2を境にして式 が異なるため,(2) は左の解 答のような合計4通りの場 合分けが必要になってくる。 1=|| 4 4 A 2 I 1 T 0 1 2 3 4 X 0 1234 x 参考 (2)のグラフは, 式の意味を考える方法でかくこともできる。 [1] f(x) が2未満なら2倍する。 [2] f(x) が2以上4以下なら, 8から2倍を引く。 [右図で,黒の太線 細線部分が y=f(x), 赤の実線部分が ソ=f(f(x)) のグラフである。] なお, f(f(x))をf(x) とf(x) の 合成関数 といい, (ff)(x) と書く (詳しくは数学Ⅲで学ぶ)。 8から2倍を 引く 4 2 0 2倍する 4 x で

解決済み 回答数: 1