Question 257120
Here is the original problem:
{{{x^2-4xy+4y^2-z^2+8z-16}}}
step 1 - group the first 3 and the last 3 like this:
{{{(x^2-4xy+4y^2)-(z^2-8z+16)}}}
Notice we had to change the signs on the last 3 because we factored out a negative.
step 2 - factor the first group and the second group separately as
{{{(x-2y)^2 - (z-4)^2}}}
step 3 - notice we now have difference of 2 squares, so we factor to get
{{{(x - 2y + z - 4)(x-2y -z + 4)}}}