You can't do much simplifying with these, but I want you to get used to the notation because it will show up in Calculus:  find the slopes

Graph of a line that passes through the points ( a , f( a ) ) and ( x , f( x ) )

 
Graph of a line that passes through the points ( x , f( x ) ) and ( x + h , f( x + h ) )

*simplify the
 denominator

Does your answer on this last one look familiar?  (I'll talk about it more later.)