倪éãããšè±åããã¯,å
çããåºãããæ¬¡ã®åé¡ã«ã€ããŠèããŠããã
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座æšå¹³é¢äžã«5ç¹A(1,6), B(2,7), C(-2,-9), D(-4,-9), E (-7,21) ãããã
(i) 2æ¬¡é¢æ°y=f(x) ã®ã°ã©ãã, 3ç¹ A, B, Cãéãã f(x) ãæ±ããã
(ii) 2æ¬¡é¢æ°y=g(x)ã®ã°ã©ãã, 3ç¹C,D,Eãéãã g(x) ãæ±ããã
倪é: f(x) 㯠2æ¬¡é¢æ°ã ãšããã£ãŠãããã,f(x)=ax2+bx+c ãšãããŠèšç®ããã°, a,b,c
ã®å€ãæ±ããããšãã§ãããã ãã
è±å: f(x)ã¯2æ¬¡é¢æ°ã ããã 㢠ãšããæ¡ä»¶ãå¿
èŠã ãã
倪é: ããã ã£ããã 3ç¹ãéãæ¡ä»¶ãé ã«
a+b+c=
ã€
ãŠ
a+
I |b+c=7
㪠a- ã«
b+c=-9
ã ããããã®é£ç«æ¹çšåŒãè§£ããš, α = ã㯠6ã±
C=
ãšæ±ãŸããã
ã§ã, (ii)ã§åãããšãããããšãããš, èšç®ãé¢åã ãã
è±å 2æ¬¡é¢æ°ã®ã°ã©ãã®å¯Ÿç§°æ§ã䜿ããšããå°ãããŸãã§ãããã ãã
倪é : ãããã«, 2ç¹C, Dã®y座æšãçãããšããããšãã
g(x)= ãµ
ãšããããšãã§ãããã
è±å: g(x) = | ãµ ãšããæ¹ã, (i)ãšåãããã«ãããããèšç®ã楜ã«ã§ãããã ãã
(1)~ã³ã«åœãŠã¯ãŸãæ°ãæ±ããã
㢠ã®è§£ç矀
â© a=1 â a=-2 2a=0
â¢a> o ⣠a<0
ãµ ã®è§£ç矀
â© d(x-3)2-9 â d(x-3)2 +q
⡠d(x+3)2-9 ⢠d(x+3) +q
1