Let's start out working with the numerator f(x) - f(1)  only:

f(x) - f(1) =  -  =  - · =  -  = 

Now let's divide that by the denominator x - 1:

÷ = ÷ = · 

Now we have to play a trick with the 

1 - x

First arrange it in descending order

-x + 1

Factor out -1

-1(x - 1)

Now replace the 1 - x by that in  · 

·

Cancel the (x - 1)'s

·



Edwin