x4 - 10x2 + 9 x2 - 10x + 9 x4 - x2 + 3 2x4 - 10x2 + 19
This can be solved using the foil method, in which you multiply the FIRST, OUTER, INNER, and then LAST variables together.
(x - 1) * (x + 1) * (x - 3) * (x + 3)
(x^2 - 1^2) * (x^2 - 3^2)
(x^2 - 1) * (x^2 - 9)
x^4 - 9x^2 - x^2 + 9
x^4 - 10x^2 + 9