I think you left off the 2 coefficient and also you left
the square root symbol off of the 7 in what you 
multiplied by.
 To find out what to multiply by,
take the denominator,
To find out what to multiply by,
take the denominator,  Change the sign of the SECOND term, so that
you have
Change the sign of the SECOND term, so that
you have  Now put that over itself:
  
Now put that over itself: so that it will just equal to 1 and therefore
it won't affect the value of the original 
problem when we multiply by it.
so that it will just equal to 1 and therefore
it won't affect the value of the original 
problem when we multiply by it.


 Put parentheses around all numerators and denominators:
Put parentheses around all numerators and denominators:


 Indicate the multiplication of the numerators and
denominators, so that we just have one fraction:
Indicate the multiplication of the numerators and
denominators, so that we just have one fraction:
 FOIL out the top and bottom:
FOIL out the top and bottom:
 The middle two tems in the bottom cancel out:
The middle two tems in the bottom cancel out:
 Take square roots of 9 and 49, which are 3 and 7:
Take square roots of 9 and 49, which are 3 and 7:
 
 
 Edwin
Edwin