题目

(16分)已知工厂生产某种产品，次品率p与日产量x（万件）间的关系为 ，每生产1件合格产品盈利3元，每出现1件次品亏损1.5元． （I）将日盈利额y（万元）表示为日产量（万件）的函数；（Ⅱ）为使日盈利额最大，日产量应为多少万件? 答案：解：（Ⅰ）当时，，    当， 日盈利额y（万元）与日产量x（万件）的函数关系为 ； （Ⅱ）由（Ⅰ）知，当时，日盈利额为0.当时，， ， 令得或（舍去） ①当时，，在区间上单调递增， ，此时； ②当时，在（0，3）上，，在（3，6）上， ， 综上，若，则当日产量为c万件时，日盈利额最大； 若，则One afternoon, Kate and her brother Bob went out to play.Kate was eight, and Bob was ten.“Let’s go to the bridge and we can see fish in the river.” said Kate.“I don’t know…” Bob said.“Mum told us, ‘don’t go on the bridge.’ She said it’s dangerous.”Kate said, “I am not afraid.Are you?”They walked onto the bridge and began looking for fish in the river.The bridge was a train bridge.Trains went over the bridge three times a day.The children were standing in the middle of the bridge when they heard a loud noise.“A train is coming!” Bob shouted.“Run!” He ran to the end of the bridge.He was safe.Kate ran, too, but she fell.The train was coming fast.Kate ran towards Bob.She fell again right on the train tracks(铁轨).There was no time to leave.She had to lie down between the tracks.A few seconds later, the train went over the girl, but she was not hurt at all.She stood up and said to Bob, “Don’t tell Mum! Don’t tell Mum!”At last their mother found out about the story.She was angry because they went on the bridge.But she was happy that Kate was all right.【小题1】 Bob and Kate were       .A．twinsB．brothersC．sistersD．brother and sister【小题2】One afternoon they went to the bridge to see       .A．their motherB．fishC．the trainD．the river【小题3】When the train came, the children were       .A．in the middle of the bridgeB．at the end of the bridgeC．on their way to the bridgeD．away from the bridge【小题4】Where was Kate when the train was going over her?A．She fell again right on the train tracks(铁轨).B．Kate ran towards Bob.C．She had to lie down between the tracks.D．She stood up and cried.【小题5】When their mother knew about the story, she was       .A．happyB．angryC．sorryD．both angry and happy