# Simple Factoring Question

• May 20th 2007, 08:58 AM
Masterigor
Simple Factoring Question
Hello, I need to factor 4x^4-5x^2-9 and I'm not sure how to do it.
The closest I got was:
(2x^2+3)(2x^2-3)-5X^2

but I wasn't sure what do do with the -5X^2. I also tried:

4x^4-5x^2-9
X^2(4x^2 -5)-3^2

But then I wasn't sure what to do with the 9. Can someone please direct me as to what I am doing wrong or how to do the problem? Thanks
• May 20th 2007, 09:05 AM
Jhevon
Quote:

Originally Posted by Masterigor
Hello, I need to factor 4x^4-5x^2-9 and I'm not sure how to do it.
The closest I got was:
(2x^2+3)(2x^2-3)-5X^2

but I wasn't sure what do do with the -5X^2. I also tried:

4x^4-5x^2-9
X^2(4x^2 -5)-3^2

But then I wasn't sure what to do with the 9. Can someone please direct me as to what I am doing wrong or how to do the problem? Thanks

did you notice that this was a quadratic in x^2 ?

4x^4 - 5x^2 - 9 = 4(x^2)^2 - 5(x^2) - 9
if we let x^2 = y, we get:

4y^2 - 5y - 9
can you take it from here?