Answer:

Explanation:
The expression we are given is

We factor the denominator of each expression.
To factor 
x²-x-12, we find factors of -12 that sum to -1.
-4(3) = -12 and -4+3 = -1; this gives us

Cancelling the common factors in the numerator and denominator, we have

To factor 
x²-8x+16, we find factors of 16 that sum to -8; 
-4(-4) = 16 and -4+-4 = -8. This gives us

Cancelling the common factors in the numerator and denominator, we have

This gives us
