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Mathematics Junior High

四角で囲った部分はなぜこのような式になるのですか?

テーマ 19 面積を分割する 放物線y=212x2と直線y=x+bとの交点を, x座標の小さい方からそれぞれA,Bとしたとき, 点のx座標は-1である。 また, 直線y=x + b とx軸との交点をC, 原点を0とする。 (1) 6 の値を求めなさい。 (2) AOBと△ADB の面積が等しくなるよう に,放物線上の2点A,Bの間に点Dをとる とき, Dの座標を求めなさい。 (3) 点Cを通り △ADB の面積を2等分する直線 と 直線BD との交点のx座標を求めなさい。 [解説] (1) 点Aは放物線上の点だから, A (-1. 1/21) これを直線y=x+bの式に代入して, 1 3 2 = -1 + 6,b= (2) 等積変形・神技 61 (本冊 P.118) を利用する。 原点Oを通り直線ABと平行な直線y=x を 1 引き、y=-2xとの交点がDである。 1 - x² = x 2 x2-2x=0 x(x-2)=0 x=2 D (2, 2) Just 2+(3-2) X 1 7 3 3 解答D (22) y= 2 m2 (3) 神技 65b (本冊 P.128) を利用する。 求める点をPとする。 x座標の差から BC:CA=3:1だから, APC = Sとす れば, △BPC = 3S となる。 直線CP により ADB の面積は2等分されるのだから, 四 角形CADP = 3S で, △PAD = 四角形 CADP-APC =3S-S=2S よって, DP: PB = △PAD: △PAB = 2S:4S = 1:2 つまり, Pのx座標は, A(-1,2) =-=1/√x² -2 y = 12 A YA ・1 O O S A (-1, -1/-) B 〈慶應義塾湘南藤沢高等部〉 問題 P.131 ③3 |解答 y=x+b 3S D (2, 2) 2S y=x+ y=x b = x P B 13. D (2, 2) 3 2 7 テーマ 1 19 面積を分割する

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Mathematics Junior High

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Do you like dogss OU He dogs7 People ay tha dogs ae me oldew fiends orhumans Some 所 Te Vi People as Pets o tnlk about some Dogs we led by many peopls。 Now Tm gomg kinds of dogs w 「 Tes Working fordiabled peopkk。 They are not pes。 Toy are saiiance dogE 1p Japan。 there are three kinds of assistanee dogs。 They are gnide dogs。 service doB3 and Teng dogy Tody。 jn Japan。 more tan a momsand ssshtance dogs work for diabled PeoPIe To of thom are guide dogs。 The mumber of senrice dogs and hearing dogs is mot So large 人 OF Mey 1 2017。 here were onby abowe seveny senoe dogs mm Japan。 The number of hearing dogs was about he same. Guide dogs work for peopls who cannot see。 Guide dogs lead thc users when hy 8O 9 Herent places。 The dogs walk with the uscrs and gnuide them im a sefc way。 For Purposc。 guide dogs are ( A ) to go stmight along the road。 The users know hhe situaon j front of them thanks to the dogs、 and give dmectoons to the dogsy such as Wai FComer md “Sright go.” We can say that a gnide dog and the user work together to walk safely。 Service dogs work for people who cannot use their ams or legs ficcly。 Scrvice dogs do a Jot of things in daily lives for such people. For example。 they pick up things on the floor opcn. and close doors, and bring things from other places。 When something dangerous happens。 the dog can even run to some other people and ask thcm for hclp。 We can say that service dogs [で①語 Hearing dogs work for pcople who cannot hear。 Haring dogs can understand many kinds or sounds。 such as phones alanm clocksr cping babics nd so on。 The dogs 【 by /tel/ is heard / usi ig / thc users / their / what sound 】bodies: ER lece。 the dogs ouch the users and lead them to the place。 Hearing dogs can tcll many kinds of sonnds to the users and help them The law about assistance dogs says that they can go with the users imto many places Hike Testanrants, supenmarkets, and so on. So you have many chances to see thcm。 But you should amember one important thing about them。 Assiance dogs are not pets。 They are working 5r the users. so you must not talk to them or touch them。 OF course you must not give them ay food. Asshtance dogs md the usems respect eech othier ss Partnets。 When you meet an ssistance dog and te uscr in town。 just see what they dO。 TF they need some help。 lers ghve them a hand.

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Mathematics Junior High

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Do you like dogss OU He dogs7 People ay tha dogs ae me oldew fiends orhumans Some 所 Te Vi People as Pets o tnlk about some Dogs we led by many peopls。 Now Tm gomg kinds of dogs w 「 Tes Working fordiabled peopkk。 They are not pes。 Toy are saiiance dogE 1p Japan。 there are three kinds of assistanee dogs。 They are gnide dogs。 service doB3 and Teng dogy Tody。 jn Japan。 more tan a momsand ssshtance dogs work for diabled PeoPIe To of thom are guide dogs。 The mumber of senrice dogs and hearing dogs is mot So large 人 OF Mey 1 2017。 here were onby abowe seveny senoe dogs mm Japan。 The number of hearing dogs was about he same. Guide dogs work for peopls who cannot see。 Guide dogs lead thc users when hy 8O 9 Herent places。 The dogs walk with the uscrs and gnuide them im a sefc way。 For Purposc。 guide dogs are ( A ) to go stmight along the road。 The users know hhe situaon j front of them thanks to the dogs、 and give dmectoons to the dogsy such as Wai FComer md “Sright go.” We can say that a gnide dog and the user work together to walk safely。 Service dogs work for people who cannot use their ams or legs ficcly。 Scrvice dogs do a Jot of things in daily lives for such people. For example。 they pick up things on the floor opcn. and close doors, and bring things from other places。 When something dangerous happens。 the dog can even run to some other people and ask thcm for hclp。 We can say that service dogs [で①語 Hearing dogs work for pcople who cannot hear。 Haring dogs can understand many kinds or sounds。 such as phones alanm clocksr cping babics nd so on。 The dogs 【 by /tel/ is heard / usi ig / thc users / their / what sound 】bodies: ER lece。 the dogs ouch the users and lead them to the place。 Hearing dogs can tcll many kinds of sonnds to the users and help them The law about assistance dogs says that they can go with the users imto many places Hike Testanrants, supenmarkets, and so on. So you have many chances to see thcm。 But you should amember one important thing about them。 Assiance dogs are not pets。 They are working 5r the users. so you must not talk to them or touch them。 OF course you must not give them ay food. Asshtance dogs md the usems respect eech othier ss Partnets。 When you meet an ssistance dog and te uscr in town。 just see what they dO。 TF they need some help。 lers ghve them a hand.

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