Question 238896
Hello,
When we're dealing with factors, it simply means something multiplied by something else. With this problem   t^4-81 it can be shown as: 
(t^2-9)(t^2+9) If you notice the (t^2-9) can be factored even more to:
(t-3)(t+3) so now we have 3 factors as shown here:
(t-3)(t+3)(t^2+9) and there's the answer. 
RJ Toftness
www.math-unlock.com