ÌâÄ¿ÄÚÈÝ
ÏÈÔĶÁ£¬ÔÙ½â´ð£º
·½³Ìx2-3x-4=0µÄ¸ùÊÇ£ºx1=-1£¬Ôò£¬x1x2=-4£»
·½³Ì3x2+10x+8=0µÄ¸ùÊÇ£ºx1=-2£¬x2=-
£¬Ôòx1+x2=-
£¬x1x2=
£®
£¨1£©Èôx1£¬x2ÊÇ·½³Ìax2+bx+c=0µÄ¸ù£¬Ôòx1+x2=
£»£¨ÓÃa¡¢b¡¢c±íʾ£©
£¨2£©Èç¹ûx1£¬x2ÊÇ·½³Ìx2+x-3=0µÄÁ½¸ö¸ù£¬¸ù¾Ý£¨1£©ËùµÃ½áÂÛ£¬Çó
+
µÄÖµ£®
·½³Ìx2-3x-4=0µÄ¸ùÊÇ£ºx1=-1£¬Ôò£¬x1x2=-4£»
·½³Ì3x2+10x+8=0µÄ¸ùÊÇ£ºx1=-2£¬x2=-
4 |
3 |
10 |
3 |
8 |
3 |
£¨1£©Èôx1£¬x2ÊÇ·½³Ìax2+bx+c=0µÄ¸ù£¬Ôòx1+x2=
-
b |
a |
-
£¬x1x2=b |
a |
c |
a |
c |
a |
£¨2£©Èç¹ûx1£¬x2ÊÇ·½³Ìx2+x-3=0µÄÁ½¸ö¸ù£¬¸ù¾Ý£¨1£©ËùµÃ½áÂÛ£¬Çó
x | 2 1 |
x | 2 2 |
·ÖÎö£º£¨1£©ÓÉÒÑÖªÖÐÁ½¸ùÖ®ºÍÓëÁ½¸ùÖ®»ýµÄ½á¹û¿ÉÒÔ¿´³ö£¬Á½¸ùÖ®ºÍÕýºÃµÈÓÚÒ»´ÎÏîϵÊýÓë¶þ´ÎÏîϵÊýÖ®±ÈµÄÏà·´Êý£¬Á½¸ùÖ®»ýÕýºÃµÈÓÚ³£ÊýÏîÓë¶þ´ÎÏîϵÊýÖ®±È£¬µÃ³ö¼´¿É£»
£¨2£©ÏÈ°Ñ´úÊýʽx12+x22±äÐÎΪÁ½¸ùÖ®»ý»òÁ½¸ùÖ®ºÍµÄÐÎʽ£¬È»ºóÓëÁ½¸ùÖ®ºÍ¹«Ê½¡¢Á½¸ùÖ®»ý¹«Ê½Çó³ö¼´¿É£®
£¨2£©ÏÈ°Ñ´úÊýʽx12+x22±äÐÎΪÁ½¸ùÖ®»ý»òÁ½¸ùÖ®ºÍµÄÐÎʽ£¬È»ºóÓëÁ½¸ùÖ®ºÍ¹«Ê½¡¢Á½¸ùÖ®»ý¹«Ê½Çó³ö¼´¿É£®
½â´ð£º½â£º£¨1£©ÓÉÒÑÖªµÃ³ö£ºx1+x2=-
£¬x1x2=
£¬
¹Ê´ð°¸Îª£º-
£¬
£»
£¨2£©¡ßx1£¬x2ÊÇ·½³Ìx2+x-3=0µÄÁ½¸ö¸ù£¬
¡àx1+x2=-
=-1£¬x1x2=
=-3£¬
¡à
+
=£¨x1+x2£©2-2x1x2=1+6=7£®
b |
a |
c |
a |
¹Ê´ð°¸Îª£º-
b |
a |
c |
a |
£¨2£©¡ßx1£¬x2ÊÇ·½³Ìx2+x-3=0µÄÁ½¸ö¸ù£¬
¡àx1+x2=-
b |
a |
c |
a |
¡à
x | 2 1 |
x | 2 2 |
µãÆÀ£º±¾Ì⿼²éÁ˸ùÓëϵÊýµÄ¹Øϵ£¬½«¸ùÓëϵÊýµÄ¹ØϵÓë´úÊýʽ±äÐÎÏà½áºÏ½âÌâÊÇÒ»ÖÖ¾³£Ê¹ÓõĽâÌâ·½·¨£®
Á·Ï°²áϵÁдð°¸
Ïà¹ØÌâÄ¿