f(x+1)=f(x)+1/x(x+1),x属于N*正整数且f(l)=3,求f(x)

f(x)=f(x-1)+1/(x-1)-1/x
f(x-1)=f(x-2)+1/(x-2)-1/(x-1)
.
f(2)=f(1)+1-1/2
叠加,得f(x)=f(1)+1+1/(x-1)-1/x