Question 173654
16x^4 - 40x^2 + 9 = 
This is what I came up with: 
8(2x^4 - 5x^2) + 1 is this correct?
.
No
if you expanded your equation:
8(2x^4 - 5x^2) + 1
You would get:
16x^4 - 40x^2 + 1
Which is NOT the same as what you started with.
.
The correct solution is:
16x^4 - 40x^2 + 9
(4x^2-1)(4x^2-9)
.
Can't stop here either because it can be further factored:
(4x^2-1)(4x^2-9)
(2x+1)(2x-1)(2x-3)(2x+3)