Question

Which of the following ate factors of t^4-81

Answer 1

`Use:\ a^2-b^2=(a-b)(a+b)\\------------------\\t^4-81=(t^2)^2=9^2=(t^2-9)(t^2+9)\\\\=(t^2-3^2)(t^2+9)=(t-3)(t+3)(t^2+9)`