题目

某企业打算建造一个池底为正方形，深度为2m的长方体无盖水池.已知水池壁的造价为100元/m2，水池底的造价为200元/m2，总造价为6400元.求这个正方形水池底的边长． 答案：【答案】正方形池底的边长为4m．【解析】根据题意设池底边长为xm，再根据工程总造价列方程解得池底边长.设正方形池底的边长为xm． 由题意，可得200x2+100×（4×2x）=6400 整理，得x2+4x﹣32=0．∴（x﹣4）（x+8）=0，∴x1=4，x2=﹣8（不合题意，舍去）答：正方形池底的边长为4m．The oil in your car          ．You'd better drive to the gas station and fill it up．A．has run out                                             B．is running outC．is using up                                              D．has been run out of