What is the completely factored form of x4 + 8x2 – 9? a(x + 1)(x – 1)(x + 3)(x + 3) b(x + 1)(x - 1)(x2 + 9) c(x2 – 1)(x + 3)(x – 3) d(x + 1)(x + 1)(x + 3)(x + 3)

ANSWER

The correct answer is B

EXPLANATION

We want to factor completely,


We can rewrite the above expression in the form.



We can think of this expression as a quadratic trinomial in


We need to split the middle term with factors of -9 that adds up to 8.



We factorize to obtain,



We factor further to obtain,



We apply difference of two squares on the leftmost factor to obtain,