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我们知道,对于可导函数求极值问题,首先求导,让导数为0,求出可疑极值点.但有些函数的导函数为超越函数,其零点(可疑极值点)很难求出,这时我们可以采用设而不求的思想加以处理,本文举例说明设而不求思想在函数求极值中的应用.例1(2013年新课标卷Ⅱ理科第21题第(2)问)已知函数f(x)=ex-ln(x+m),当m≤2时,证明f(x)>0.
We know that for the derivation of a derivable function, we first derive the derivative, let the derivative be zero, and find the suspicious extreme. However, the derivatives of some functions are transcendental and its zero (suspicious extreme) is hard to find , Then we can use this instead of thinking to be dealt with, this article illustrates the use of set without thinking in the function of the extreme value of the application.Example 1 (2013 New Curriculum Volume II Science Section 21 (2) Q) The function f (x) = ex-ln (x + m) is known. When m≤2, f (x)> 0 is proved.