ÌâÄ¿ÄÚÈÝ
13£®Ä³ÎÀÊÓ×ÛÒÕ½ÚÄ¿ÖÐÓÐÒ»¸ö»·½Ú½Ð¡°³¬¼¶²Â²Â²Â¡±£¬¹æÔòÈçÏ£ºÔÚÕâÒ»»·½ÚÖмαöÐèÒª²ÂÈýµÀÌâÄ¿£¬ÈôÈýµÀÌâÄ¿Öв¶ÔÒ»µÀÌâÄ¿¿ÉµÃ1·Ö£¬Èô²Â¶Ô2µÀÌâÄ¿¿ÉµÃ3·Ö£¬ÒªÊÇÈýµÀÌâÄ¿ÍêÈ«²Â¶Ô¿ÉµÃ6·Ö£¬ÈôÈýµÀÌâÄ¿È«²¿²Â´í£¬Ôò¿Ûµô4·Ö£®Èç¹û¼Î±ö²Â¶ÔÕâÈýµÀÌâÄ¿µÄ¸ÅÂÊ·Ö±ðΪ$\frac{2}{3}¡¢\frac{1}{2}¡¢\frac{1}{3}$£¬ÇÒÈýµÀÌâÄ¿Ö®¼äÏ໥¶ÀÁ¢£®Çó£ºÄ³¼Î±öÔڸá°²ÂÌ⡱»·½ÚÖÐËùµÃ·ÖÊýµÄ·Ö²¼ÁÐÓëÊýѧÆÚÍû£®·ÖÎö ÓÉÌâÒâÉèX±íʾ¸Ã¼Î±öËùµÃ·ÖÊý£¬ÔòX¿ÉÈ¡¾ö£¬1£¬3£¬6£¬·Ö±ðÇó³öÏàÓ¦µÄ¸ÅÂÊ£¬ÓÉ´ËÄÜÇó³öij¼Î±öÔڸá°²ÂÌ⡱»·½ÚÖÐËùµÃ·ÖÊýµÄ·Ö²¼ÁÐÓëÊýѧÆÚÍû£®
½â´ð ½â£ºÓÉÌâÒâÉèX±íʾ¸Ã¼Î±öËùµÃ·ÖÊý£¬ÔòX¿ÉÈ¡1£¬3£¬6£¬
P£¨X=0£©=£¨1-$\frac{2}{3}$£©¡Á£¨1-$\frac{1}{2}$£©¡Á£¨1-$\frac{1}{3}$£©=$\frac{1}{9}$£¬
P£¨X=1£©=$\frac{2}{3}¡Á\frac{1}{2}¡Á\frac{2}{3}+\frac{1}{3}¡Á\frac{1}{2}¡Á\frac{2}{3}+\frac{1}{3}¡Á\frac{1}{2}¡Á\frac{1}{3}$=$\frac{7}{18}$£¬
P£¨X=2£©=$\frac{2}{3}¡Á\frac{1}{2}¡Á\frac{2}{3}+\frac{2}{3}¡Á\frac{1}{2}¡Á\frac{1}{3}+\frac{1}{3}¡Á\frac{1}{2}¡Á\frac{1}{3}$=$\frac{7}{18}$£¬
P£¨X=3£©=$\frac{2}{3}¡Á\frac{1}{2}¡Á\frac{1}{3}$=$\frac{1}{9}$£¬
¡àXµÄ·Ö²¼ÁÐΪ£º
X | -4 | 1 | 3 | 6 |
P | $\frac{1}{9}$ | $\frac{7}{18}$ | $\frac{7}{18}$ | $\frac{1}{9}$ |
µãÆÀ ±¾Ì⿼²éÀëÉ¢ÐÍËæ»ú±äÁ¿µÄ·Ö²¼ÁкÍÊýѧÆÚÍûµÄÇ󷨣¬ÊÇÖеµÌ⣬½âÌâʱҪÈÏÕæÉóÌ⣬עÒâ¸ÅÂÊ֪ʶµÄºÏÀíÔËÓã®
A£® | 30ÖÖ | B£® | 90ÖÖ | C£® | 180ÖÖ | D£® | 270ÖÖ |
A£® | $\frac{3}{5}$ | B£® | $\frac{4}{5}$ | C£® | $\frac{4}{5}$ | D£® | -$\frac{4}{3}$ |