Question 1182006

Keller performed the work below to express the polynomial in factored form:	
r(x) = x4  -  8x2  -  9 	
r(x) = (x2 + 1)(x2  -  9) 
(x) = (x + 1)(x  -  1)(x + 3)(x  -  3)
Explain the error he made and complete the factorization correctly.
<pre>x + 1 and x - 1 are <b><u>NOT</b></u> factors of x<sup>2</sup> + 1. 
Having said that, can you now provide the correct factorization?