Verified Answer :

MattD

You bring to a common denominator and the numerator and denominator oversimplifying:
\(\frac{1}{x}+\frac{1}{x+h}=\frac{1*(x+h)}{x(x+h)}+\frac{1*x}{x(x+h)}=\frac{2x+h}{x(x+h)}\)

1/x+1/x+h
=1(x+h)/x(x+h)+1x/x(x+h)
=2x+h/x(x+h)