设0则f(x1)-f(x2)=(x1-x2)-(x1-x2)/(x1x2)=(x1-x2)[1-1/(x1x2)]当0则(x1-x2)[1-1/(x1x2)]＞0此时f(x1)＞f(x2)即x属于(0,1)时，f(x)是减函数当10。且x1-x2＜0则(x1-x2)[1-1/(x1x2)]＜0此时f(x1)＜f(x2)即x属于(1，正无穷大)时，f(x)是增函数
