導(dǎo)數(shù)法是運(yùn)用導(dǎo)數(shù)知識(shí)解答問(wèn)題的方法.導(dǎo)數(shù)法是解答函數(shù)問(wèn)題的重要方法，尤其在解答函數(shù)單調(diào)性問(wèn)題、圖象問(wèn)題、最值問(wèn)題、不等式問(wèn)題時(shí)，靈活運(yùn)用導(dǎo)數(shù)法，可化難為易、化繁為簡(jiǎn).那么如何巧妙運(yùn)用導(dǎo)數(shù)法來(lái)解答函數(shù)問(wèn)題呢？下面結(jié)合實(shí)例進(jìn)行探討.

一、函數(shù)單調(diào)性問(wèn)題

函數(shù)單調(diào)性問(wèn)題的常見(jiàn)命題形式有： （1）判斷函數(shù)的單調(diào)性； （2）求函數(shù)的單調(diào)區(qū)間； （3）由函數(shù)的單調(diào)性求參數(shù)的取值范圍.對(duì)于簡(jiǎn)單的函數(shù)單調(diào)性問(wèn)題，一般可用函數(shù)單調(diào)性的定義或基本初等函數(shù)的單調(diào)性求解.而對(duì)于較為復(fù)雜的函數(shù)單調(diào)性問(wèn)題，往往需運(yùn)用導(dǎo)數(shù)法求解.首先對(duì)函數(shù)的解析式求導(dǎo)；然后令導(dǎo)函數(shù)為0，求得零點(diǎn)；再用零點(diǎn)將函數(shù)的定義域劃分為幾個(gè)子區(qū)間，并在各個(gè)子區(qū)間上討論導(dǎo)函數(shù)的符號(hào).一般地，在某區(qū)間上的導(dǎo)函數(shù)大于0，則函數(shù)在該區(qū)間上單調(diào)遞增；在某區(qū)間上的導(dǎo)函數(shù)小于0，則函數(shù)在該區(qū)間上單調(diào)遞減.