ʱ : һ 专题8《二次函数的图像与性质》教案与练习 - 百度文库ϿʼĶ
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纯y?ax2?bx?c(a?0)ΪκʵκҲж.
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ߵĽʽõʽ 1һʽy?ax?bx?c(a?0)
2ʽy?a(x?h)?k(a?0)(h,k)ߵĶꡣ
3ʽy?a(x?x1)(x?x2)(a?0)ʽֻxнʱõʽx1x2xύĺꡣ
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1 Ϊy?x2?kx?k?1иkֵ 1ߵĶxϣ 2ߵĶyϣ 3ߵĶ??1,?2? 4߾ԭ㣻
5x?1ʱyСֵ 6yСֵΪ?1.
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2 ֱy?kx?by?ax2ĺֱΪx1x2ֱxύĺΪx3֤
111??. x1x2x322⣺x1x2Ϊkx?b?axax?kx?b?0
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k1b?? bx3k111?? x1x2x312ʱֵ25ax?bx?c?0??23 κy?ax2?bx?cx?????19abc
33⣺κy?a(x?h)?k(a?0)
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1124 ֤aȡκʵֵʱy?x?(a?1)x?a?ͨһ㣬Щ
24ߵx?ߵĶ㶼һȷϡ ֤y?x?(a?1)x?x??2111111a??x2?x??a(x?)?(x?)2?a(x?) 24422211ʱa(x?)?0,y?0 22aȡκʵʱ֪ͨM???1?,0? ?2?ͽ -- й͡רҵСѧԴŻվ Ȩ@ͽ
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11?a?1?12y?x?(a?1)x?a???x???a
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⣺߹?0,4?,?2,?2?㣬ʽb??2a?3,c?4 y?ax2?bx?c?ax2?(2a?3)x?4
249?4??2(a?0)
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92ߵĽʽy?x?12x?4
2xϽصõ߶γɱʾΪ
6 κy?ax2?bx?cͼĶ?2,4?ֱy?x?4yཻPQR㣬PQ:QR=1:3κʽ ⣺ͼĶ?2,4?Կy?a(x?2)2?4 1
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7 ֪y??x2?px?qxڵAByڵC֡ACB=90,tanCAOtanCBO2.
1ߵĽʽ
2ƽxֱ߽ڵMNǷMNΪֱxеԲڣ˵ɣڣԲİ뾶
1ߵĽʽpqֵһ棬pq뷽x2?px?q?0ϵһq߶OCijOC2?OA?OB,OAOBǷx2?px?q?0ľֵʹpqܽϵpq
2Ǵ⣬ԲͼֱۿԲıضߵĶԳϣҰ뾶Բĵľֵ
1ABĺֱΪx1,x2x1,x2Ƿx2?px?q?0x1?0?x2
x1?x2?px1x2??q?0
RtABCУOCΪбABϵĸߣ OC2?OA?OB?x1x2?q ֡OC?q q?q
Ϊ߲ԭ㣬q?0,q?1 ǺĶx1?0?x2ã
222y C OC1OC1?? tanCBO?? AOx1BOx2x?x11 裬????12?2x1?x2??2x1x2
x1x2x1x2 x1?x2?p,x1x2??q??1 p2
tanCAO
ߵýʽΪy??x2?2x?1
2A O B x 2MNΪ?x3,r?,?x4,r?x3,x4Ƿr??x?2x?1?x?2x?r?1?0
2
x3?x4?2,x3x4?r?1 MN?x3?x4?
(x3?x4)2?4x3x4?4?4(r?1)?22?r ԲxУԲڣ
1MN?r2?r?r 2̵ⷽãrr2??2 1?1Բİ뾶Ϊ12.
˵Ǵǡεۺ⣬漰κ̡ǺRtȶ֪ʶ.
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