(2)初項から第n項までの和 Snを求めよ。

39. 点Bの座標をB(X, Y)とすると, 線分 ABの X+1 Y+5 中点の座標は 2 |2 これが,直線 上にあるから Y+5 1 X+1 +2 2 2 2- すなわち Y=X-- の 2 また,線分 AB と直線lは直交するから Y-5 1 X-1 2 すなわち Y=-2X+7 … のを2に代入すると -1 2 =-2X+7 2

取り組み日 再点 月 目標時間 STEP3 読解問題にアプローチ (2年7月改) 20分 The Latin word infans, from which “infant" comes, means "a person who is unable to speak" But all mothers know that communication begins long before actual speech. Babies “talk" to parents with their eyes, their expressions and their whole bodies, and parents respond to them in the same language. Human beings are different from other animals in our highly developed use of language and understanding. Ababy can hear conversations even while she is in her mother's womb. And then from the minute she is born she begins to feel the rhythms of her native language and gradually learns to recognize meaning. In South Africa, *the Bantu tribe celebrates the first time a child answers to her name witha special dinner. The best way to encourage your baby's language is to begin a two*way conversation. Mothers all over the world talk to their babies in a special language, known as "(ア)motherese" or “baby talk". Without learning how, we tend to use the simplest words, changing our grammar to make sentences shorter. Mothers talk of themselves in the third person, repeat things, and speak to their infants in a sing-song pitch. By looking at our babies while we are talking to them, we also teach them the facial expressions that come with speech. Babies start babbling from around three months, repeating easy sounds like “da", “ta", "ma", “ba" and “pa”. All around the world these first basic sounds are the roots of common names for other family members, most importantly “mother" and “father". For example, baba means “mother” among *the Gusii tribe of Kenya, while baban is “father" for *the Sambarivo people of Madagascar. The English word “daddy" is tata in Greek, tatasin Sanskrit and papa in French. Considering the amount of time she spends with her baby in the first months, a mother might expect her baby to say her name first. But this doesn't usually happen. Studies have shown that (イ)babies try to name their fathers before their mothers. Perhaps mothers want to hear their baby's first word as “daddy", in order to make a father feel more important and to add more meaning to his fatherhood. Or perhaps father, a familiar but often a little more distant person, is considered worth saying first. In Europe, the origins of the everyday words for “mother" are closely related to breastfeeding. Mom, Mam, Mummy - all these words come fronm the ancient Greek mamman, which means 17

(月 日) 得 11 複素数と方程式(1) 261. (1) 1+2i , 2-i 3-4i を簡単にせよ。ただし, iは虚数単位を表す。 (10点) 5i (2) 実数x, yについて (3+i)x+(2-3i)y=8-iが成り立つとき, x, yの値を求めよ ただし、iは虚数単位である。 (10点)

4 1 a,6を定数とする. xの2次関数 f(x)= x°-2ax+ b について,0Sxs2 における最大値を M, 最小値を mとする. (1) a=1, b==3 とする. 原をーαとす 天了 (i)放物線 y=f(x) の頂点の座標を求めよ。 るす[-=D () 来国()M, および mをそれぞれ求めよ. (2) b=3 のとき, mをaの値で場合分けして求めよ。 (3) 0Sas2 のとき, 0<xs2 における(ソ=f(x)の値域が 0<ys2 となる 調のような a, bの値の組 (a, b) をすべて求めよ。 同: の

35. S=1+2-3+3·32+433 +… …+n-3"-1 とお くと BS=1-3+2-3?+3-3*+………+(n-1)3"-1+n-3" 初々を引くと -2S=D1+3+3° +3°+ +3ー1-n.3" 3"-1 (1-2n)3-1 ーn.3"= 3-1 2 よって S=2n-1)3" +1 4

34. Hは辺 AB上の点であるから, tを実数として OH=ta+(1-)b (0<t<1)と表される。 AB=4から6-a=D4° 2 ゆえに,b|-2a·b+la|"=16であるから 2°-24-b+(/10)=16 したがって a.石=-1 OHLABであるから OH.AB=0 よって OH-AB={ta +(1-:信-石) da+(1-)b+(2t-1)a·b =-10t+4(1-t)ー(2t-1)=-16t+5=0 |2 ニー 5 ゆえに,t= 16 であるから OH=4+。 11 一 -b 16 16