Question 650256
Here is how to factor {{{b^4-16)

First, we need to find the square root of {{{b^4}}} that is {{{b^2}}}
Next, we need to be able to get the square root of 16, that is 4. We will use a positive and negative 4. Why, because -4*+4=-16

{{{(b^2+4)(b^2-4)}}}

Hope this helps you!

Dr. Sheldon Cooper