How would the fraction, 7/1- square root of 5, be rewritten if its denominator is rationalized using difference of squares?

You say you meant " 7/1 - square root of 5 "   OK.  I will interpret that to be:

     7 

 1 - sqrt(5)

If you wish to rationalize the denominator, mult. both the numerator and the denom. of the above fraction by 1 + sqrt(5).  You will get:

  7( 1+sqrt(5) )        7( 1+sqrt(5) )
=
     1^2 - 5                       -4