Hi guys, help me figure out what I'm doing wrong. The problem is 36-9x^4-4x^2+x^6, I factorise it by grouping and I get 9-x^2, which apears to be the correct answer. However, in my text book the answer is (x^2 +2)(x−√2)(x+√2)(x−3)(x+3) ... Please help me out, what steps i need to follow to get to that result?
Start with 36-9x^4-4x^2+x^6, and factorise.
x^6 - 9x^4 - 4x^2 + 36
x^4(x^2 - 9) - 4(x^2 - 9)
(x^4 - 4)(x^2 - 9)
(x^2 + 2)(x^2 - 2)(x^2 + 3)(x^2 - 3)
(x^2 +2)(x−√2)(x+√2)(x+3)(x−3)