how do you factor 16x^4 - 40x^2 + 9 I don't understand how the factoring should go. When I think of a way to factor it it doesn't turn out right.

Question

how do you factor 16x^4 - 40x^2 + 9 I don't understand how the factoring should go.  When I think of a way to factor it it doesn't turn out right.

Reiny · Answer

(4x^2 - 9)(2x^2 - 1) = (2x + 3)(2x - 3)(2x^2 - 1)

drwls · Answer

16x^4 - 40x^2 + 9 = (4x^2 -9)(4x^2 -1) = (2x+3)(2x-3)(2x+1)(2x-1)

Selena · Answer

16x^2-121