first take x+h and sub into function, then subtract off f(x)
7/[4(x+h)-3] - 7/[4x-3] / h
clear your complex fraction by multiplying numerator and denominator by
[4x + 4h -3][4x -3] leaving you with
7[4x-3] - 7[4x+4h-3] / h[4x-3][4x+4h-3]
distribute the numerator parenthesis, terms will cancel leaving you with 1 term in numerator involving an h, you can cancel the h
-28/[4x+4h-3][4x-3]
this is usually connected with a limit as h approaches 0, definition of a derivative
Hopefully this helps.[/tex]