Question 418173
<pre><font face = "DFKai-SB" color = "indigo" size = 4><b>
{{{(f+1)/(f-1)}}}{{{"÷"}}}{{{(3f+3)/(f-9)}}}

Invert the second fraction and change the division 
to multiplication:

{{{(f+1)/(f-1)}}}{{{"×"}}}{{{(f-9)/(3f+3)}}}

Indicate the multiplications of the tops and bottoms:

{{{((f+1)(f-9))/((f-1)(3f+3))}}}

Factor 3 out of (3f+3):

{{{((f+1)(f-9))/((f-1)3(f+1))}}}

Cancel the (f+1)'s:

{{{((cross(f+1))(f-9))/((f-1)3(cross(f+1)))}}}

{{{(f-9)/((f-1)3)}}}

Move the 3 in front on the bottom:

{{{(f-9)/(3(f-1))}}}

or if you like you can distribute the bottom:

{{{(f-9)/(3f-3)}}}

Edwin</pre>