证明设x1,x2属于（-1,+∞）且x1＜x2则f（x1）-f（x2）=1/（x1+1）-1/(x2+1)=（x2+1）/（x2+1）（x1+1）-（x1+1）/（x1+1）(x2+1)=（x2-x1）/（x2+1）（x1+1）由x1,x2属于（-1,+∞）且x1＜x2即x1+1＞0,x2+1＞0,x1-x2...