如何证明1- 1/(x+1)≤In(x+1)
2个回答

令f(x)=In(x+1)+1/(x+1)-1,(x>-1)

求导得f'(x)=1/(x+1)-1/(x+1)^2=x/(x+1)^2

当-10

所以当x=0时,f(x)取得最小值,即f(x)min=f(0)=0

从而有f(x)≥f(x)min=0

即In(x+1)+1/(x+1)-1≥0

1- 1/(x+1)≤In(x+1)