(Ⅰ)φ(x)=x
1
x=e
1
xlnx,∴φ′(x)=x
1
x•[1-lnx
x2,
φ′(1)=1,φ(1)=1,∴φ(x)=x
1/x](x>0)在x=1处的切线方程为y=x.
令φ′(x)=0得x=e,当x∈(0,e)时,φ′(x)>0,φ(x)单调递增,
当x∈(e,+∞)时,φ′(x)<0,φ(x)单调递减,
∴φ(x)在(0,e)时,单调递增,在(e,+∞)时,单调递减.
(Ⅱ)方程φ′(x)=φ(x)([1
x2-
a/x]+[a-1/2])等价于x
1
x•[1-lnx
x2=x
1/x]([1
x2-
a/x]+[a-1/2]),
即[a-1/2x2-ax+lnx=0,设g(x)=
a-1
2x2-ax+lnx (x>0),
∴g′(x)=(a-1)x-a+
1
x]=
(a-1)x2-ax+1
x,
①当a=1时,g′(x)=[1-x/x],x∈(0,1)时,g′(x)>0,g(x)递增,x∈(1,+∞)时,g′(x)<0,g(x)递减,
[g(x)]max=g(1)=-1<0,此时方程无实数根;
②当a>1时,g′(x)=(a-1)x-a+[1/x]=
(a-1)x2-ax+1
x=
(a-1)(x-