please simplify

(1/1+x+h) - (1 /1+x ) divided by h

1/(1+x+h) - 1/(1+x)

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

Now divide that by h and you have

-1/((1+x+h)(1+x))