ÇëÔĶÁÏÂÃæ²ÄÁÏ£º
ÈôA£¨x
1£¬y
£©£¬B£¨x
2£¬y
£© ÊÇÅ×ÎïÏßy=ax
2+bx+c£¨a¡Ù0£©Éϲ»Í¬µÄÁ½µã£¬Ö¤Ã÷Ö±Ïß
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103201018647465339/SYS201311032010186474653021_ST/0.png)
Ϊ´ËÅ×ÎïÏߵĶԳÆÖᣮ
ÓÐÒ»ÖÖ·½·¨Ö¤Ã÷ÈçÏ£º
¢Ù¢Ú
Ö¤Ã÷£º¡ßA£¨x
1£¬y
£©£¬B£¨x
2£¬y
£© ÊÇÅ×ÎïÏßy=ax
2+bx+c£¨a¡Ù0£©Éϲ»Í¬µÄÁ½µã
¡à
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103201018647465339/SYS201311032010186474653021_ST/1.png)
ÇÒ x
1¡Ùx
2£®
¢Ù-¢ÚµÃ a£¨x
12-x
22£©+b£¨x
1-x
2£©=0£®
¡à£¨x
1-x
2£©[a£¨x
1+x
2£©+b]=0£®
¡à
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103201018647465339/SYS201311032010186474653021_ST/2.png)
ÓÖ¡ßÅ×ÎïÏßy=ax
2+bx+c£¨a¡Ù0£©µÄ¶Ô³ÆÖáΪ
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103201018647465339/SYS201311032010186474653021_ST/3.png)
£¬
¡àÖ±Ïß
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103201018647465339/SYS201311032010186474653021_ST/4.png)
Ϊ´ËÅ×ÎïÏߵĶԳÆÖᣮ
£¨1£©·´Ö®£¬Èç¹ûM£¨x
1£¬y
1£©£¬N£¨x
2£¬y
2£© ÊÇÅ×ÎïÏßy=ax
2+bx+c£¨a¡Ù0£©Éϲ»Í¬µÄÁ½µã£¬Ö±Ïß
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103201018647465339/SYS201311032010186474653021_ST/5.png)
Ϊ¸ÃÅ×ÎïÏߵĶԳÆÖᣬÄÇô×Ô±äÁ¿È¡x
1£¬x
2ʱº¯ÊýÖµÏàµÈÂð£¿Ð´³öÄãµÄ²ÂÏ룬²¢²Î¿¼ÉÏÊö·½·¨Ð´³öÖ¤Ã÷¹ý³Ì£»
£¨2£©ÀûÓÃÒÔÉϽáÂÛ½â´ðÏÂÃæÎÊÌ⣺
ÒÑÖª¶þ´Îº¯Êýy=x
2+bx-1µ±x=4ʱµÄº¯ÊýÖµÓëx=2007ʱµÄº¯ÊýÖµÏàµÈ£¬Çóx=2012ʱµÄº¯ÊýÖµ£®