17£®ÏÈÔĶÁÏÂÁвÄÁÏ£¬È»ºó½â´ðÎÊÌ⣺
²ÄÁÏ£º´Ó4ÕŲ»Í¬µÄ¿¨Æ¬ÖÐÑ¡È¡2ÕÅ£¬ÓÐ6ÖÖ²»Í¬µÄÑ¡·¨£¬³éÏó³ÉÊýѧÎÊÌâ¾ÍÊÇ´Ó4¸ö²»Í¬ÔªËØÖÐÑ¡È¡2¸öÔªËصÄ×éºÏ£¬×éºÏÊý¼ÇΪ${C}_{4}^{2}$=$\frac{4¡Á3}{2¡Á1}$=6£®Ò»°ãµØ£¬´Ón¸ö²»Í¬ÔªËØÖÐÑ¡È¡m¸öÔªËصÄ×éºÏÊý¼Ç×÷${C}_{n}^{m}$£¬${C}_{n}^{m}$=$\frac{n£¨n-1£©£¨n-2£©¡­£¨n-m+1£©}{m£¨m-1£©£¨m-2£©¡­2¡Á1}$£¨m¡Ün£©£®
ÀýÈ磺´Ó6¸ö²»Í¬ÔªËØÖÐÑ¡3¸öÔªËصÄ×éºÏ£¬×éºÏÊý¼Ç×÷${C}_{6}^{3}$=$\frac{6¡Á5¡Á4}{3¡Á2¡Á1}$=20
£¨1£©ÎªÓ­½Ó¹ú¼Ò½¨É蹤×÷¼ì²é£¬Ñ§Ð£½«¾Ù°ìСÐÍÊé»­Õ¹ÀÀ£®ÍõÀÏʦÔڰ༶8·ùÓÅÐãÊé»­ÖÐÑ¡È¡3·ù£¬¹²ÓжàÉÙÖÖÑ¡·¨£¿
£¨2£©Ì½Ë÷·¢ÏÖ£º
¼ÆË㣺${C}_{3}^{2}$=3£¬${C}_{3}^{3}$=1£¬${C}_{4}^{3}$=4£¬${C}_{5}^{3}$=10£¬${C}_{5}^{4}$=5£¬${C}_{6}^{4}$=15£®
ÓÉÉÏÊö¼ÆË㣬ÊÔ²ÂÏë${C}_{n}^{k}$£¬${C}_{n}^{k+1}$£¬${C}_{n+1}^{k+1}$Ö®¼äÓÐʲô¹Øϵ£®£¨Ö»Ð´½áÂÛ£¬²»Ðè˵Ã÷ÀíÓÉ£©
£¨3£©ÇëÄãÖ±½ÓÀûÓã¨2£©ÖвÂÏëµÄ½áÂÛ¼ÆË㣺${C}_{4}^{3}$+${C}_{4}^{2}$+${C}_{5}^{2}$+${C}_{6}^{2}$+¡­+${C}_{10}^{2}$£®

·ÖÎö £¨1£©¸ù¾Ý²ÄÁϸø³öµÄ·½·¨Ö±½Ó¼ÆËã¼´¿É£»
£¨2£©¸ù¾Ýж¨Òå·Ö±ð½øÐмÆË㣻ÀûÓüÆËã½á¹ûµÃ${C}_{3}^{2}$+${C}_{3}^{3}$=${C}_{4}^{3}$£¬Óɴ˹æÂɿɵÃ${C}_{n}^{k}$+${C}_{n}^{k+1}$=${C}_{n+1}^{k+1}$Ö®£»
£¨3£©ÀûÓã¨2£©ÖеĹæÂÉ´Ó×óµ½ÓÒÒÀ´Î¼ÆËã¼´¿É£®

½â´ð ½â£º£¨1£©${C}_{8}^{3}$=$\frac{8¡Á7¡Á6}{3¡Á2¡Á1}$=56
´ð£º¹²ÓÐ56ÖÖÑ¡·¨£® 
£¨2£©${C}_{3}^{2}$=3£¬${C}_{3}^{3}$=1£¬${C}_{4}^{3}$=4£¬${C}_{5}^{3}$=10£¬${C}_{5}^{4}$=5£¬${C}_{6}^{4}$=15£¬
ÒòΪ${C}_{3}^{2}$+${C}_{3}^{3}$=${C}_{4}^{3}$£¬${C}_{5}^{3}$+${C}_{5}^{4}$=${C}_{6}^{4}$£¬
ËùÒÔCkn+Cnk+1=Cn+1k+1£®      
£¨3£©${C}_{4}^{3}$+${C}_{4}^{2}$+${C}_{5}^{2}$+${C}_{6}^{2}$+¡­+${C}_{10}^{2}$
=${C}_{5}^{3}$+${C}_{5}^{2}$+${C}_{6}^{2}$+¡­+${C}_{10}^{2}$
=${C}_{6}^{3}$+¡­+${C}_{10}^{2}$
=${C}_{11}^{3}$
=$\frac{11¡Á10¡Á9}{3¡Á2¡Á1}$
=165£®

µãÆÀ ´ËÌ⿼²éÊý×ֵı仯¹æÂÉ£¬ÈÏÕæ¹Û²ì¡¢×Ðϸ˼¿¼£¬ÉÆÓÃÁªÏëÊǽâ¾öÕâÀàÎÊÌâµÄ·½·¨£¬¹Ø¼üÊǶÔж¨ÒåµÄÀí½â£®

Á·Ï°²áϵÁдð°¸
Ïà¹ØÏ°Ìâ

¿ÆÄ¿£º³õÖÐÊýѧ À´Ô´£º ÌâÐÍ£º½â´ðÌâ

7£®°´ÒªÇó»Ø´ðÏÂÁи÷Ì⣺
£¨1£©Í¼1ÖÐÊÇÓɼ¸¸öСÁ¢·½¿é´î³ÉµÄ¼¸ºÎÌåµÄ¸©ÊÓͼ£¬Ð¡Õý·½ÐÎÖеÄÊý×Ö±íʾÔÚ¸ÃλÖõÄСÁ¢·½¿éµÄ¸öÊý£¬Çë»­³öÕâ¸ö¼¸ºÎÌåµÄÖ÷ÊÓͼºÍ×óÊÓͼ£®
Ö÷ÊÓͼ           ×óÊÓͼ£®
£¨2£©ÓÃСÁ¢·½¿é´î³ÉµÄ¼¸ºÎÌ壬Ö÷ÊÓͼºÍ¸©ÊÓͼÈçͼ2£¬ÎÊËü×î¶àÐèÒª13¸öСÁ¢·½¿é£¬×îÉÙÐèÒª9¸öСÁ¢·½¿é£®

²é¿´´ð°¸ºÍ½âÎö>>

¿ÆÄ¿£º³õÖÐÊýѧ À´Ô´£º ÌâÐÍ£º½â´ðÌâ

8£®ÒÑÖª£ºÈçͼ£¬Rt¡÷ABCÖУ¬¡ÏABC=90¡ã£¬ÒÔABΪ¡ÑOµÄÖ±¾¶×÷Ô²½»ACÓÚµãD£¬EÊÇBCµÄÖе㣬Á¬½ÓDE£®
£¨1£©ÇóÖ¤£ºDEÊÇ¡ÑOµÄÇÐÏߣ®
£¨2£©ÈôAB=3£¬BC=4£¬Çó¡÷DECµÄÃæ»ý£®

²é¿´´ð°¸ºÍ½âÎö>>

¿ÆÄ¿£º³õÖÐÊýѧ À´Ô´£º ÌâÐÍ£ºÌî¿ÕÌâ

5£®£¨-1.98£©¡Á£¨-3£©4¡Â237¡Á0=0£®

²é¿´´ð°¸ºÍ½âÎö>>

¿ÆÄ¿£º³õÖÐÊýѧ À´Ô´£º ÌâÐÍ£º½â´ðÌâ

12£®Èçͼ£¬ABΪ¡ÑOµÄÖ±¾¶£¬µãCÊÇ¡ÑOÉÏÒ»µã£¬BDƽ·Ö½ÇCBA½»¡ÑOÓÚµãD£¬¹ýµãD×÷Ö±ÏßFE´¹Ö±BC£¬´¹×ãΪH£¬ÇóÖ¤£ºFEÊÇ¡ÑOµÄÇÐÏߣ®

²é¿´´ð°¸ºÍ½âÎö>>

¿ÆÄ¿£º³õÖÐÊýѧ À´Ô´£º ÌâÐÍ£º½â´ðÌâ

2£®Èçͼ1Ëùʾ£¬µãE¡¢FÔÚÏ߶ÎACÉÏ£¬¹ýE£¬F·Ö±ð×÷DE¡ÍAC£¬BF¡ÍAC£¬´¹×ã·Ö±ðΪµãE£¬F£»DE£¬BF·Ö±ðÔÚÏ߶ÎACµÄÁ½²à£¬ÇÒAE=CF£¬AB=CD£¬BDÓëACÏཻÓÚµãG£®
£¨1£©ÇóÖ¤£ºEG=GF£»
£¨2£©ÈôµãEÔÚFµÄÓұߣ¬Èçͼ2ʱ£¬ÆäÓàÌõ¼þ²»±ä£¬ÉÏÊö½áÂÛÊÇ·ñ³ÉÁ¢£¿Çë˵Ã÷ÀíÓÉ£®
£¨3£©ÈôµãE¡¢F·Ö±ðÔÚÏ߶ÎCAµÄÑÓ³¤ÏßÓë·´ÏòÑÓ³¤ÏßÉÏ£¬ÆäÓàÌõ¼þ²»±ä£¬£¨1£©ÖнáÂÛÊÇ·ñ³ÉÁ¢£¿£¨ÒªÇó£ºÔÚ±¸ÓÃͼÖл­³öͼÐΣ¬Ö±½ÓÅжϣ¬²»±Ø˵Ã÷ÀíÓÉ£©

²é¿´´ð°¸ºÍ½âÎö>>

¿ÆÄ¿£º³õÖÐÊýѧ À´Ô´£º ÌâÐÍ£ºÌî¿ÕÌâ

9£®ÒÑÖªOBƽ·Ö¡ÏAOC£¬
£¨1£©Èô¡ÏAOC=64¡ã£¬Ôò¡ÏAOB=32¡ã£»
£¨2£©Èô¡ÏAOB=25.5¡ã£¬Ôò¡ÏAOC=51¡ã£®

²é¿´´ð°¸ºÍ½âÎö>>

¿ÆÄ¿£º³õÖÐÊýѧ À´Ô´£º ÌâÐÍ£ºÑ¡ÔñÌâ

6£®ÈçͼËùʾ£¬¡÷ABCÄÚ½ÓÓÚ¡ÑO£¬AB=100£¬¡ÏACB=45¡ã£¬Ôò¡ÑOµÄÖ±¾¶Îª£¨¡¡¡¡£©
A£®50$\sqrt{2}$B£®100$\sqrt{2}$C£®150$\sqrt{2}$D£®200$\sqrt{2}$

²é¿´´ð°¸ºÍ½âÎö>>

¿ÆÄ¿£º³õÖÐÊýѧ À´Ô´£º ÌâÐÍ£ºÌî¿ÕÌâ

7£®ÀÏʦÔÚºÚ°åÉÏ»­ÁËÒ»ÌõÖ±ÏßABºÍABÍâÒ»µãP£¬Ïë¹ýµãP×÷Á½ÌõÖ±ÏßCD¡¢EF£¬ÈôCD¡ÎAB£¬ÕâʱEFÓëABµÄλÖùØϵÊÇÏཻ£®

²é¿´´ð°¸ºÍ½âÎö>>

ͬ²½Á·Ï°²á´ð°¸