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数学 高校生

⑵と⑶について質問です。 kの値による場合分けをする必要があるときとないときの違いがわからないので教えてください。

場合 代入 - 1 る。 整数 i 理数 なお, もの 基本例題 40 2次方程式の解の判別 KATABLADO 次の2次方程式の解の種類を判別せよ。 ただし, kは定数とする。 (1) 3x²-5x+3=0 (2) 2x²-(k+2)x+k-1=0 (3) x2+2(k-1)x-k+4k-3=0 /p.71 基本事項 2 2次方程式 ax2+bx+c=0の解の種類は,解を求めなくても、判別式 D の符号だけ で判別できる。 2次方程式の解の判別 DO異なる2つの実数解 b D=0⇔重 解 重解はx=- -za) 2a D< 0 ⇔ 異なる2つの虚数解 (2),(3) 文字係数の2次方程式の場合も,解の種類の判別方針は, (1) と変わらないが, Dがんの2次式で表され,kの値による場合分けが必要となることがある。 与えられた2次方程式の判別式をDとすると 解答(1) D=(-5)-4・3・3=-11<0 よって, 異なる2つの虚数解をもつ。 (2) D={-(k+2)}^-4・2(k-1) =k+4k+4-8(k-1) =k²-4k+12=(k-2)^+8 ゆえに, すべての実数んについて よって異なる2つの実数解をもつ。 (3) 2=(k-1)^-1・(-k²+4k-3)=2k²-6k+4 =2(k²-3k+2)=2(k-1)(k-2) よって, 方程式の解は次のようになる。 D0 すなわち k<1,2くんのとき 異なる2つの実数解 D = 0 すなわち k=1, 2 のとき 重解 D< 0 すなわち 1 <k<2のとき 異なる2つの虚数解 -D<0- √ DOV 2 -DX01 (4) x²-(k-3)x+k²+4=0 カフェ {-(+2)}^の部分は, D>0 ・D > 0 - k 08- (-1)' =1なので, (+2)2 と書いてもよい。 ax²+2b'x+c=0 では D 12c を利用する。 (5) x²-(k-2)x+ 4 α<βのとき (x-a)(x-B)>0 ⇔x<a, B<x 練習 次の2次方程式の解の種類を判別せよ。 ただし, kは定数とする。 ②40 (1) x23x+1=0 (2) 4x²-12x+9=0 k 2 α<βのとき (x-a)(x-β)<0 ⇔α<x<B (3) -13x2+12x-3=0 E +5=0 2章 2 ⑧ 2次方程式の解と判別式

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英語 中学生

この答えあっていますか? 1、Futoshi is often go to river 2、Hi give to yukata 英語苦手です…

7 これを読んで、後の問いに答えなさい。 次の英文は、 Futoshiがホームスティを体験したことについて書かれた文章です。 Futoshi is a junior high school student. Last summer he went to New Zealand for two weeks to study English. He stayed with a family there. They were Mr. and Mrs. Green and their son, Tom. Tom was as old as Futoshi. One day, at breakfast, Tom said. "Fishing is very popular in New Zealand. Do you like to go fishing, Futoshi?" Futoshi said, "Yes, I often go fishing with my family in Japan." Then Mr. Green said, "That's good. We have a boat) Do you want to go fishing with us in the sea tomorrow, Futoshi?" Futoshi said, "Yes. I often go fishing in the river and the lake, but not in the sea. I really want to do that with you. Thank you." The next day, Futoshi went fishing with Tom and his family on the boat. The weather was very good. There were no clouds in the blue sky and the sun was (shining. And the sea was blue and clear. Everything was so beautiful. Futoshi felt very happy. Tom said, "Look, Futoshi. Some dolphins are swimming over there." Futoshi said, "Wow, greatl This is my first time to see dolphins in the sea. It's so exciting!" Then Mr. Green said, "OK. Let's start fishing now." Tom and his After about twenty minutes, Futoshi got a big fish. He said, "Oh, this is very big. I have never got a big fish like this." Tom said, "You are great, Futoshi." family also got some fish. At lunch time, Mr. and Mrs. Green cooked some of the fish they got. Under the blue sky, Futoshi ate them with his host family on the boat. One night, Futoshi showed a yukata to Tom and his family. Futoshi said. "This is a present for Mrs. Green. It is a traditional Japanese dress called yukata in Japanese. Yukata is a kind of kimono. You can see a lot of people in yukata at summer festivals in Japan." Futoshi taught her how to put on the yukata. When she put on the yukata, she said, "How do I look? Futoshi said "You look beautifull" And then she said, "This is nice, but it's difficult for me to walk in this yukata." (1) 次の①、②の問いに、英語で答えなさい。 Where did Futoshi often go fishing in Japan? What was given to Mrs. Green by Futoshi?

解決済み 回答数: 1