ÌâÄ¿ÄÚÈÝ
13£®Àí¿Æ¾ºÈüС×éÓÐ9ÃûÅ®Éú¡¢12ÃûÄÐÉú£¬´ÓÖÐËæ»ú³éȡһ¸öÈÝÁ¿Îª7µÄÑù±¾½øÐзÖÎö£®£¨¢ñ£©Èç¹û°´ÕÕÐÔ±ð±ÈÀý·Ö²ã³éÑù£¬¿ÉÒԵõ½¶àÉÙ¸ö²»Í¬µÄÑù±¾£¿£¨Ð´³öËãʽ¼´¿É£©
£¨¢ò£©Èç¹ûËæ»ú³éÈ¡µÄ7ÃûͬѧµÄÎïÀí¡¢»¯Ñ§³É¼¨£¨µ¥Î»£º·Ö£©¶ÔÓ¦Èç±í£º
| ѧÉúÐòºÅ | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
| ÎïÀí³É¼¨ | 65 | 70 | 75 | 81 | 85 | 87 | 93 |
| »¯Ñ§³É¼¨ | 72 | 68 | 80 | 85 | 90 | 86 | 91 |
·ÖÎö £¨¢ñ£©Èç¹û°´ÕÕÐÔ±ð±ÈÀý·Ö²ã³éÑù£¬Ôò´Ó9ÃûÅ®Éú¡¢12ÃûÄÐÉú£¬´ÓÖÐËæ»ú³éȡһ¸öÈÝÁ¿Îª7µÄÑù±¾£¬³éÈ¡µÄÅ®ÉúΪ3ÈË£¬ÄÐÉúΪ4ÈË£®ÀûÓÃ×éºÏÊýµÄÒâÒå¼´¿ÉµÃ³ö£®
£¨II£©Õâ7ÃûͬѧÖÐÎïÀíºÍ»¯Ñ§³É¼¨¾ùΪÓÅÐãµÄÈËÊýΪ3ÈË£¬³éÈ¡µÄ3ÃûͬѧÖÐÎïÀíºÍ»¯Ñ§³É¼¨¾ùΪÓÅÐãµÄÈËÊýX¿ÉÄÜȡֵΪ0£¬1£¬2£¬3£¬¿ÉµÃP£¨X=k£©=$\frac{{∁}_{3}^{k}{∁}_{4}^{3-k}}{{∁}_{7}^{3}}$£¬¼´¿ÉµÃ³ö·Ö²¼ÁÐÓëÊýѧÆÚÍû¼ÆË㹫ʽ£®
½â´ð ½â£º£¨¢ñ£©Èç¹û°´ÕÕÐÔ±ð±ÈÀý·Ö²ã³éÑù£¬Ôò´Ó9ÃûÅ®Éú¡¢12ÃûÄÐÉú£¬
´ÓÖÐËæ»ú³éȡһ¸öÈÝÁ¿Îª7µÄÑù±¾£¬³éÈ¡µÄÅ®ÉúΪ3ÈË£¬ÄÐÉúΪ4ÈË£®¿ÉÒԵõ½${∁}_{9}^{3}{∁}_{12}^{4}$¸ö²»Í¬µÄÑù±¾£®
£¨II£©Õâ7ÃûͬѧÖÐÎïÀíºÍ»¯Ñ§³É¼¨¾ùΪÓÅÐãµÄÈËÊýΪ3ÈË£¬
³éÈ¡µÄ3ÃûͬѧÖÐÎïÀíºÍ»¯Ñ§³É¼¨¾ùΪÓÅÐãµÄÈËÊýX¿ÉÄÜȡֵΪ0£¬1£¬2£¬3£¬
ÔòP£¨X=k£©=$\frac{{∁}_{3}^{k}{∁}_{4}^{3-k}}{{∁}_{7}^{3}}$£¬¿ÉµÃP£¨X=0£©=$\frac{4}{35}$£¬P£¨X=1£©=$\frac{18}{35}$£¬P£¨X=2£©=$\frac{12}{35}$£¬P£¨X=3£©=$\frac{1}{35}$£®
ÆäX·Ö²¼ÁÐΪ£º
| X | 0 | 1 | 2 | 3 |
| P | $\frac{4}{35}$ | $\frac{18}{35}$ | $\frac{12}{35}$ | $\frac{1}{35}$ |
µãÆÀ ±¾Ì⿼²éÁ˳¬¼¸ºÎ·Ö²¼ÁеĸÅÂÊÊýѧÆÚÍû¼°Æä·½²îµÄ¼ÆË㹫ʽ¡¢×éºÏÊýÓë³Ë·¨¼ÆÊýÔÀí¼ÆË㹫ʽ£¬¿¼²éÁËÍÆÀíÄÜÁ¦Óë¼ÆËãÄÜÁ¦£¬ÊôÓÚÖеµÌ⣮
| A£® | -x4 | B£® | -3x4+2 | C£® | x4-2 | D£® | 4x4-5 |
| A£® | 7 | B£® | 8 | C£® | 9 | D£® | 11 |
| A£® | £¨-$\frac{1}{2}$£¬+¡Þ£© | B£® | [-$\frac{1}{2}$£¬+¡Þ£© | C£® | £¨0£¬+¡Þ£© | D£® | [0£¬+¡Þ£© |
| A£® | $£¨¡À\sqrt{2}£¬0£©$ | B£® | $£¨0£¬¡À\sqrt{2}£©$ | C£® | £¨0£¬¡À2£© | D£® | £¨¡À2£¬0£© |