y=(x+1)^10*e^(-x)对x求导:y'=[(x+1)^10]'*e^(-x)+(x+1)^10*[e^(-x)]'y'=[10(x+1)^9]e^(-x)-[(x+1)^10]e^(-x)y'=e^(-x)*[10(x+1)^9-(x+1)^10]y'=e^(-x)*(x+1)^9*[10-(x+1)]令y'=0即有:x1=-1,x2=9因此x...
f(x)二阶可导,f(π)=0,f''(π)>0,x=π是f(x)的极值点,g(x)=f(x)cosx,则x=π是g(x)的极大值还是极小值,还是它的极值点
g'(x)=f'(x)cosx-f(x)sinx则g'(π)=0,x=π为驻点g''(x)=f''(x)cosx-f'(x)sinx-f'(x)sinx-f(x)cosx则g''(π)=f''(π)cosπ-0-0-0=f''(π)cosπ=-f''(π)