已知函數(shù)f(x)=a(x)3+3(x)2-x+1在R上是減函數(shù),求a的取值范圍(3,2為次數(shù))

熱心網(wǎng)友

f(x)=a(x)3+3(x)2-x+1f`(x)=3ax^2+6x-1f（x）為減函數(shù)，f`(x)在R上恒小于0即3ax^2+6x-1=0a<0

熱心網(wǎng)友

用導(dǎo)數(shù)求