The concentration of a certain chemical in a full water tank depends on the depth of the water. At a depth that is x feet below the top of the tank, the concentration is (3加上根号5-x分之4） parts per million, where 0<x<4. To the nearest 0.1 foot, at what depth is the concentration equal to 6 parts per million? A 2.4ft B 2.5ft C2.8ft D3.0ft E3.2ft
不太明白题目中的" to the nearest 0.1 foot''是什么意思，还有请写出解题思路， 答案是E
3加上根号5-x分之4=6,得出x=3.2. 实际就是一个函数题，告诉你函数的表达式以及因变量，让你求自变量~to the nearest 0.1foot就是让你四舍五入时，保留一位小数。 昨天碰到一个题说是to the nearest 10,那也就是说197时则四舍五入成200,193时四舍五入成190.
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发表于 2012-8-9 16:37:53
(3加上根号5-x分之4） parts per million, where 0<x<4. To the nearest 0.1 foot, at what depth is the concentration equal to 6 parts per million? A 2.4ft
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