# Thread: Need help in finding all complex solutions

1. ## Need help in finding all complex solutions

I tried working it out but I didn't get the right answer... Btw the correct answer is "B" which is highlighted.... What did I do wrong?

2. ## Re: Need help in finding all complex solutions

Originally Posted by asilvester635
I tried working it out but I didn't get the right answer... Btw the correct answer is "B" which is highlighted.... What did I do wrong?
You have the right idea, but you factored wrong. $\displaystyle (x^2)^2 - 8(x^2) - (3^2) \neq ( (x^2) - 3 )^2$. How do you factor $\displaystyle y^2 - 8y - 9$?

-Dan

3. ## Re: Need help in finding all complex solutions

$\displaystyle x^4-8x^2-9=(x^2-9)(x^2+1)$.

4. ## Re: Need help in finding all complex solutions

Originally Posted by Plato
$\displaystyle x^4-8x^2-9=(x^2-9)(x^2+1)$.
Which factorises further :P

5. ## Re: Need help in finding all complex solutions

Originally Posted by Prove It
Which factorises further :P
But why do that? The roots are perfectly obvious from that product.

6. ## Re: Need help in finding all complex solutions

Originally Posted by Plato
But why do that? The roots are perfectly obvious from that product.
To you and me perhaps, not to everyone though...