是减函数．…（2分）证明：设0＜x1＜x2＜1，…（4分）则f(x1)−f(x2)＝(x1−x2)+(1x1−1x2)=(x1−x2)(x1x2−1)x1x2，…（9分）∵0＜x1＜x2＜1，∴x1x2-1＜0，x1-x2＜0…（12分）∴f（x1）＞f（x2）．∴f（x）在（0，...