Can you help me answer this equation?

1 1
__ - __
x+h x
_______________________

h

Your algebraic expression did not get printed out in a recognizable form. It is better is you use parentheses and brackets, and try to type it in a single line. If what you are looking for is
[(1/(x+h)- 1/x]/h, then rewrite it as
(1/h)* [x - (x+h)]/[x(x+h)]
= (1/h)*(-h)/[x(x+h)]
= -1/[x(x+h)]

why are parentheses used in mathematicas????

Parentheses are used in mathematics to group operations and indicate the order in which calculations should be done. They help to clarify the meaning of an expression and ensure that it is evaluated correctly.

For example, consider the expression 3 * 2 + 4. Without parentheses, it may be unclear whether to multiply 3 by 2 first or add 4 after. But if we write it as (3 * 2) + 4, it becomes clear that the multiplication should be done first.

Parentheses also play a crucial role in algebraic equations, as they can be used to denote the numerator or denominator of a fraction, the argument of a function, or the input for specific operations.

In the original expression you provided [(1/(x+h) - 1/x]/h, parentheses are used to group the subtraction of (1/(x+h) - 1/x) first, and then the resulting expression is further divided by h. These parentheses ensure that the correct subtraction is carried out before dividing by h.