1可以通過復合函數(shù)的性質來判斷通則增，異則減2通過經驗例如，加負號改變單調性等3求導導函數(shù)確實方便而直接增函數(shù)+增函數(shù)=增函數(shù) 減函數(shù)+減函數(shù)=減函數(shù) 增函數(shù)減函數(shù)=增函數(shù) 減函數(shù)增函數(shù)=減函數(shù)。 如果函數(shù)的導數(shù)大于0，則該函數(shù)為增函數(shù)如果函數(shù)的導數(shù)小于0，則該函數(shù)為減函數(shù)例如，對于函數(shù)fx = x...