Answer :
You bring to a common denominator and the numerator and denominator oversimplifying:
[tex]\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)}[/tex]
[tex]\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)}[/tex]
