Question

simplify (1/x) + (1/(x+h)

Answer 1

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

Answer 2

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