Question 168695
x^4 - 13x^2 + 36
Factor this like an ordinary quadratic except you have:
:
(x^2 - 9)(x^2 - 4); (If you FOIL this you will get the original expression)
:
Note that each factor is the "difference of squares" and can be further factored
 (x^2 - 9) = (x - 3)(x + 3)
and
(x^2 - 4) = (x - 2)(x + 2)