Question

Which of the following are the factors of t4 – 81?

A. (t – 3)(t + 3)2
B. (t – 3)(t + 3)(t2 + 9)
C. (t2 – 9)(t2 – 9)
D. (t – 3)2(t + 3)2

Answer 1

`t^4 - 81 \\ \\ (t^2)^2 - 9^2 \\ \\ (t^2 + 9)(t^2 - 9) \\ \\ (t^2 + 9)(t^2 - 3^2) \\ \\ (t^2 + 9)(t + 3)(t - 3) \\ \\`

The final result is: B

Answer 2

`t^4 - 81 =\\\\(t^2)^2 - (9)^2=\\\\(t^2 - 9)(t^2 + 9) =\\\\\boxed{\bf{ (t-3)(t+3)(t^2 + 9)}}`

Your answer is B.