学年

質問の種類

数学 高校生

(ィ)の①の条件のk>2がどうしてでてくるのかわかりません。解説お願いします🙇‍♀️

すべての実数xについて,不等式(k-2)x+2(k-1)x+3k-5>0 が成 例題 106 絶対不等式 [2] り立つような定数kの値の範囲を求めよ。 思考プロセス 例題105との違い・・・問題文では,単に「不等式」 となっており, 「2次不等式」とは限らない。 noit AG « Action 最高次の係数が文字のときは,かどうかで場合分けせよ DARESALEDON-Setm 場合に分ける 不等式 JS 0 ② より よって ゆえに 解 f(x) = (k-2)x2+2(k-1)x+3k-5 とおく。 (ア) k=2のとき 与えられた不等式は 2x+1> 0 これはすべての実数xについて成り立つとはいえない。 2のとき (イ) >0 両辺に すべての実数xについて f(x) > 0 が成り立つのは, 2次関数y=f(x)のグラフが下に凸であり,x軸と共 有点をもたないときである。 よって, f(x)=0 の判別式をDとすると k> 2・・・ ① かつ D<0 ・・・ ② k-2=0のとき 1次関数 y= 常にx軸より上側にある。 k-20 のとき 2次関数y= 常に x軸より上側にある。 上?下? k< -2k² +9k-9 - (2k-3) (k-3) < 0 (2k-3) (k-3) > 0 3<k 3 2' D = (k − 1)² – (k − 2)(3k-5) IND 4 (8+ X) 0-(0-3)(2+8) 3 k=2, ①, ③ より k> 3 (ア), (イ) より 求めるんの値の範囲は k> 3 [グラフは□に凸の放物線 3 2 のグラフが グラフとx軸の共有点は BALATO のグラフが 2 *-=- 070 y=f(x) 例題83 x CA Fot 不等式の解は x>- に限られる。 (+) +bx+y=f(x) 下に凸 D<0 1-2 x もし, グラフが上に凸で あれば、 次の図のように f(x) となる部分が存 在する。 y=f(x) x REFER niol ●①の条件を忘れないよう にする。

解決済み 回答数: 1
英語 中学生

リーディングの問題です。 色付き下線部の英文の訳し方がよくわかりません。 どのようにして,回答のようになるのか教えて下さい🙇‍♀️

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 swimming with the children. One day they asked him to go for a swim with them./Mr. Black said "We can't go for a swim. We may never swim in the lake again." "Why not?" asked Edward. "Because the lake is polluted," said Mr. Black. "There's a new sign at the lake. It says No Swimming, Polluted." "What is polluting the lake?" asked Jill. "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 clean. “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." "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 friend 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. 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 One day (イ) came to help. 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

解決済み 回答数: 2